diff --git a/lib/masamune/schema/map.rb b/lib/masamune/schema/map.rb
index 9657952..56207e1 100644
--- a/lib/masamune/schema/map.rb
+++ b/lib/masamune/schema/map.rb
@@ -34,7 +34,7 @@ def gets(*a)
         line = __getobj__.gets(*a)
         return unless line
         return line if skip?
-        encode(line.split(separator)).join(separator)
+        encode(line, separator).join(separator)
       end
 
       private
@@ -43,12 +43,36 @@ def skip?
         @store.json_encoding == :quoted
       end
 
-      def encode(fields = [])
-        fields.map { |field| field =~ /^{|}$/ ? quote(field) : field }
+      def encode(line, separator)
+        fields = []
+        buffer = ''
+        nested = false
+        line.strip.each_char do |char|
+          case char
+          when '{'
+            buffer << char
+            nested = true
+          when '}'
+            buffer << char
+            nested = false
+          when separator
+            if nested
+              buffer << char
+            else
+              fields << quote(buffer)
+              buffer = ''
+            end
+          else
+            buffer << char
+          end
+        end
+        fields << quote(buffer)
+        fields.compact
       end
 
-      def quote(field)
-        %Q{"#{field.gsub(/(?<!")"(?!")/, '""')}"}
+      def quote(buffer)
+        return buffer if buffer =~ /\A".*"\z/
+        %Q{"#{buffer.gsub('"', '""')}"}
       end
 
       def separator
diff --git a/spec/masamune/schema/map_spec.rb b/spec/masamune/schema/map_spec.rb
index 05f6744..64b4613 100644
--- a/spec/masamune/schema/map_spec.rb
+++ b/spec/masamune/schema/map_spec.rb
@@ -538,28 +538,36 @@
 
     subject { encoder.gets }
 
-    context 'with raw json' do
+    context 'with raw empty json' do
       before do
-        io.write '{"enabled":true}'
+        io.write '{},{}'
         io.rewind
       end
-      it { is_expected.to eq(%Q{"{""enabled"":true}"}) }
+      it { is_expected.to eq(%Q{"{}","{}"}) }
     end
 
-    context 'with quoted json' do
+    context 'with raw quoted json' do
       before do
-        io.write '"{""enabled"":true}"'
+        io.write '"{}","{}"'
         io.rewind
       end
-      it { is_expected.to eq(%Q{"{""enabled"":true}"}) }
+      it { is_expected.to eq(%Q{"{}","{}"}) }
     end
 
-    context 'with partially quoted json' do
+    context 'with raw json' do
+      before do
+        io.write '{"enabled":true,"state":""}'
+        io.rewind
+      end
+      it { is_expected.to eq(%Q{"{""enabled"":true,""state"":""""}"}) }
+    end
+
+    context 'with quoted json' do
       before do
-        io.write '{""enabled"":true}'
+        io.write '"{""enabled"":true,""state"":""""}"'
         io.rewind
       end
-      it { is_expected.to eq(%Q{"{""enabled"":true}"}) }
+      it { is_expected.to eq(%Q{"{""enabled"":true,""state"":""""}"}) }
     end
   end
 end