diff --git a/src/Base/App.cpp b/src/Base/App.cpp
index f61937909..885d88cee 100644
--- a/src/Base/App.cpp
+++ b/src/Base/App.cpp
@@ -104,6 +104,7 @@ bool isNoWindowMode = false;
 bool ctrl_c_pressed = false;
 bool exitRequested = false;
 vector<string> additionalPathVariables;
+vector<string> pluginDirsAsPrefix;
 
 void onCtrl_C_Input(int)
 {
@@ -222,7 +223,11 @@ App::Impl::Impl(App* self, int& argc, char** argv, const std::string& appName, c
     mout->setPendingMode(true);
     
     AppConfig::initialize(appName, organization);
+
     pluginManager = PluginManager::instance();
+    if(auto pluginPathList = getenv("CNOID_PLUGIN_PATH")){
+        pluginManager->addPluginPathList(toUTF8(pluginPathList));
+    }
 
     ext = nullptr;
     mainWindow = nullptr;
@@ -317,7 +322,7 @@ void App::setIcon(const std::string& filename)
 void App::addPluginPath(const std::string& path)
 {
     if(!path.empty()){
-        impl->pluginManager->addPluginPath(path);
+        impl->pluginManager->addPluginPathList(path);
     }
 }
 
@@ -375,6 +380,10 @@ void App::Impl::initialize()
     optionManager->add_option(
         "--path-variable", additionalPathVariables,
         "Set a path variable in the format \"name=value\"");
+
+    optionManager->add_option(
+        "--add-plugin-dir-as-prefix", pluginDirsAsPrefix,
+        "Add a plugin directory as an install path prefix");
     
     mainWindow = MainWindow::initialize(appName, ext);
 
@@ -545,6 +554,10 @@ int App::Impl::exec()
                 doQuit = true;
             }
         }
+
+        for(auto& prefix : pluginDirsAsPrefix){
+            pluginManager->addPluginDirectoryAsPrefix(prefix);
+        }
         
         optionManager->processOptionsPhase1();
 
diff --git a/src/Base/App.h b/src/Base/App.h
index 4bea695b1..a65b01156 100644
--- a/src/Base/App.h
+++ b/src/Base/App.h
@@ -27,7 +27,9 @@ class CNOID_EXPORT App
 
     ~App();
 
+    [[deprecated("Use PluginManager::addPluginPathList")]]
     void addPluginPath(const std::string& path);
+
     bool requirePluginToCustomizeApplication(const std::string& pluginName);
 
     // Optional setting
diff --git a/src/Base/PluginManager.cpp b/src/Base/PluginManager.cpp
index adf982846..22d4d64a6 100644
--- a/src/Base/PluginManager.cpp
+++ b/src/Base/PluginManager.cpp
@@ -100,7 +100,7 @@ class PluginManager::Impl
     MainMenu* mainMenu;
 
     string pluginDirectory;
-    vector<string> pluginPaths;
+    vector<string> pluginDirectories;
     QRegExp pluginNamePattern;
 
     vector<PluginInfoPtr> allPluginInfos;
@@ -121,7 +121,7 @@ class PluginManager::Impl
     LazyCaller unloadPluginsLater;
     LazyCaller reloadPluginsLater;
 
-    void addPluginPath(const std::string& path);
+    void addPluginDirectory(const std::string& directory, bool doMakeAbsolute);
     void loadPlugins(bool doActivation);
     void scanPluginFiles(const std::string& pathString, bool isUTF8, bool isRecursive);
     void loadScannedPluginFiles(bool doActivation);
@@ -176,7 +176,7 @@ PluginManager::Impl::Impl()
     mout = MessageOut::master();
     mainMenu = nullptr;
 
-    addPluginPath(cnoid::pluginDir());
+    addPluginDirectory(cnoid::pluginDir(), false);
 
     pluginNamePattern.setPattern(
         QString(DLL_PREFIX) + "Cnoid(.+)Plugin" + DEBUG_SUFFIX + "\\." + DLL_EXTENSION);
@@ -208,27 +208,73 @@ PluginManager::Impl::~Impl()
 
 
 /**
-   @param path semicolon or colon separeted path list.
+   @param pathList semicolon or colon separeted absolute path list.
 */
-void PluginManager::addPluginPath(const std::string& pathString)
+void PluginManager::addPluginPathList(const std::string& pathList)
 {
-    for(auto& path : Tokenizer<CharSeparator<char>>(pathString, CharSeparator<char>(PATH_DELIMITER))){
-        impl->addPluginPath(path);
+    for(auto& dir : Tokenizer<CharSeparator<char>>(pathList, CharSeparator<char>(PATH_DELIMITER))){
+        impl->addPluginDirectory(dir, false);
     }
 }
-    
 
-void PluginManager::Impl::addPluginPath(const std::string& path)
+
+void PluginManager::addPluginPath(const std::string& pathList)
 {
-    pluginPaths.push_back(path);
+    addPluginPathList(pathList);
+}
+
+
+void PluginManager::addPluginDirectory(const std::string& directory)
+{
+    impl->addPluginDirectory(directory, true);
+}
+
+
+void PluginManager::Impl::addPluginDirectory(const std::string& directory, bool doMakeAbsolute)
+{
+    string directoryFromUTF8;
+    if(doMakeAbsolute){
+        directoryFromUTF8 = fromUTF8(directory);
+        filesystem::path path(directoryFromUTF8);
+        if(!path.is_absolute()){
+            string absDirectory = filesystem::absolute(path).string();
+            pluginDirectories.insert(pluginDirectories.begin(), toUTF8(absDirectory));
+#ifdef Q_OS_WIN32
+            // Add the plugin directory to PATH
+            qputenv("PATH", format("{0};{1}", absDirectory, qgetenv("PATH")).c_str());
+#endif
+            return;
+        }
+    }
+    
+    pluginDirectories.insert(pluginDirectories.begin(), directory);
     
 #ifdef Q_OS_WIN32
     // Add the plugin directory to PATH
-    qputenv("PATH", format("{0};{1}", fromUTF8(path), qgetenv("PATH")).c_str());
+    if(directoryFromUTF8.empty()){
+        directoryFromUTF8 = fromUTF8(directory);
+    }
+    qputenv("PATH", format("{0};{1}", directoryFromUTF8, qgetenv("PATH")).c_str());
 #endif
 }
 
 
+/**
+   @param directory the install prefix of the corresponding plugin module.
+*/
+void PluginManager::addPluginDirectoryAsPrefix(const std::string& prefix)
+{
+    addPluginDirectory(
+        toUTF8((filesystem::path(fromUTF8(prefix)) / CNOID_PLUGIN_SUBDIR).string()));
+}
+
+
+const std::vector<std::string> PluginManager::pluginDirectories() const
+{
+    return impl->pluginDirectories;
+}
+
+
 bool PluginManager::isStartupLoadingDisabled() const
 {
     return impl->isStartupLoadingDisabled;
@@ -252,8 +298,8 @@ void PluginManager::loadPlugins(bool doActivation)
 void PluginManager::Impl::loadPlugins(bool doActivation)
 {
     if(allPluginInfos.empty()){ // Not scanned yet
-        for(auto& path : pluginPaths){
-            scanPluginFiles(path, true, false);
+        for(auto& dir : pluginDirectories){
+            scanPluginFiles(dir, true, false);
         }
     }
     loadScannedPluginFiles(doActivation);
@@ -776,7 +822,7 @@ int PluginManager::numPlugins() const
 }
 
 
-const std::string& PluginManager::pluginPath(int index) const
+const std::string& PluginManager::pluginFile(int index) const
 {
     return impl->allPluginInfos[index]->pathString;
 }
diff --git a/src/Base/PluginManager.h b/src/Base/PluginManager.h
index 1df247694..b8f47e798 100644
--- a/src/Base/PluginManager.h
+++ b/src/Base/PluginManager.h
@@ -1,11 +1,8 @@
-/**
-   @author Shin'ichiro Nakaoka
-*/
-
 #ifndef CNOID_BASE_PLUGIN_MANAGER_H
 #define CNOID_BASE_PLUGIN_MANAGER_H
 
 #include <string>
+#include <vector>
 #include "exportdecl.h"
 
 namespace cnoid {
@@ -19,7 +16,13 @@ class CNOID_EXPORT PluginManager
 	
     ~PluginManager();
 
-    void addPluginPath(const std::string& path);
+    void addPluginPathList(const std::string& pathList);
+    [[deprecated("Use addPluginPathList")]]
+    void addPluginPath(const std::string& pathList);
+    
+    void addPluginDirectory(const std::string& directory);
+    void addPluginDirectoryAsPrefix(const std::string& prefix);
+    const std::vector<std::string> pluginDirectories() const;
     bool isStartupLoadingDisabled() const;
     void doStartupLoading();
     void loadPlugins(bool doActivation);
@@ -32,7 +35,7 @@ class CNOID_EXPORT PluginManager
     void flushMessagesTo(std::ostream& os);
 
     int numPlugins() const;
-    const std::string& pluginPath(int index) const;
+    const std::string& pluginFile(int index) const;
     const std::string& pluginName(int index) const;
 
     enum PluginStatus { NOT_LOADED, LOADED, ACTIVE, FINALIZED, UNLOADED, INVALID, CONFLICT };
diff --git a/src/Choreonoid/choreonoid.cpp b/src/Choreonoid/choreonoid.cpp
index 9dc7d13ad..cecf3d492 100644
--- a/src/Choreonoid/choreonoid.cpp
+++ b/src/Choreonoid/choreonoid.cpp
@@ -6,8 +6,6 @@
 */
 
 #include <cnoid/App>
-#include <cnoid/UTF8>
-#include <cstdlib>
 
 using namespace cnoid;
 
@@ -31,9 +29,6 @@ int main(int argc, char *argv[])
 
 int execute(cnoid::App& app)
 {
-    if(auto pluginPath = getenv("CNOID_PLUGIN_PATH")){
-        app.addPluginPath(toUTF8(pluginPath));
-    }
     app.setBuiltinProject(":/Base/project/layout.cnoid");
     return app.exec();
 }