diff --git a/lib/fluent/command/fluentd.rb b/lib/fluent/command/fluentd.rb
index c5c4684089..b3dfa4145f 100644
--- a/lib/fluent/command/fluentd.rb
+++ b/lib/fluent/command/fluentd.rb
@@ -163,6 +163,10 @@
   cmd_opts[:enable_size_metrics] = b
 }
 
+op.on('--maxstdio NUMBER', "specify maxstdio number for increasing the number of opening files at once") {|s|
+  cmd_opts[:maxstdio] = s.to_i
+}
+
 op.on('-v', '--verbose', "increase verbose level (-v: debug, -vv: trace)", TrueClass) {|b|
   return unless b
   cur_level = cmd_opts.fetch(:log_level, default_opts[:log_level])
diff --git a/lib/fluent/root_agent.rb b/lib/fluent/root_agent.rb
index 6cb60916f5..335cc6b60e 100644
--- a/lib/fluent/root_agent.rb
+++ b/lib/fluent/root_agent.rb
@@ -87,6 +87,7 @@ def initialize(log:, system_config: SystemConfig.new, start_in_parallel: false)
       @source_only_mode = SourceOnlyMode.new(system_config.with_source_only, start_in_parallel)
       @source_only_buffer_agent = nil
       @enable_input_metrics = system_config.enable_input_metrics || false
+      @maxstdio = system_config.maxstdio
 
       suppress_interval(system_config.emit_error_log_interval) unless system_config.emit_error_log_interval.nil?
     end
diff --git a/lib/fluent/supervisor.rb b/lib/fluent/supervisor.rb
index 34d9dadceb..654ac53dfc 100644
--- a/lib/fluent/supervisor.rb
+++ b/lib/fluent/supervisor.rb
@@ -641,6 +641,7 @@ def self.default_options
         conf_encoding: 'utf-8',
         disable_shared_socket: nil,
         config_file_type: :guess,
+        maxstdio: nil,
       }
     end
 
@@ -681,6 +682,7 @@ def initialize(cl_opt)
       @log_path = opt[:log_path]
       @log_rotate_age = opt[:log_rotate_age]
       @log_rotate_size = opt[:log_rotate_size]
+      @maxstdio = opt[:maxstdio]
 
       @finished = false
     end
@@ -754,6 +756,14 @@ def options
       }
     end
 
+    def setup_maxstdio
+      if Fluent.windows?
+        require "fluent/win32api"
+        Win32API._setmaxstdio(@maxstdio)
+        $log.debug "Current maxstdio is #{Win32API._getmaxstdio}"
+      end
+    end
+
     def run_worker
       Process.setproctitle("worker:#{@system_config.process_name}") if @process_name
 
@@ -766,6 +776,7 @@ def run_worker
       end
 
       install_main_process_signal_handlers
+      setup_maxstdio
 
       # This is the only log messsage for @standalone_worker
       $log.info "starting fluentd-#{Fluent::VERSION} without supervision", pid: Process.pid, ruby: RUBY_VERSION if @standalone_worker
diff --git a/lib/fluent/system_config.rb b/lib/fluent/system_config.rb
index 630a8ae28f..5fec28b112 100644
--- a/lib/fluent/system_config.rb
+++ b/lib/fluent/system_config.rb
@@ -30,7 +30,7 @@ class SystemConfig
       :file_permission, :dir_permission, :counter_server, :counter_client,
       :strict_config_value, :enable_msgpack_time_support, :disable_shared_socket,
       :metrics, :enable_input_metrics, :enable_size_metrics, :enable_jit, :source_only_buffer,
-      :config_include_dir
+      :config_include_dir, :maxstdio
     ]
 
     config_param :workers,   :integer, default: 1
@@ -61,6 +61,7 @@ class SystemConfig
       v.to_i(8)
     end
     config_param :config_include_dir, default: Fluent::DEFAULT_CONFIG_INCLUDE_DIR
+    config_param :maxstdio, :integer, default: nil
     config_section :log, required: false, init: true, multi: false do
       config_param :path, :string, default: nil
       config_param :format, :enum, list: [:text, :json], default: :text
diff --git a/lib/fluent/win32api.rb b/lib/fluent/win32api.rb
index d7757a8370..41621d7660 100644
--- a/lib/fluent/win32api.rb
+++ b/lib/fluent/win32api.rb
@@ -34,5 +34,7 @@ module Win32API
     extern "intptr_t _get_osfhandle(int)"
     extern "BOOL GetFileInformationByHandle(HANDLE, void *)"
     extern "BOOL GetFileInformationByHandleEx(HANDLE, int, void *, DWORD)"
+    extern 'int _setmaxstdio(int)'
+    extern 'int _getmaxstdio(void)'
   end if Fluent.windows?
 end
diff --git a/test/config/test_system_config.rb b/test/config/test_system_config.rb
index 9a37a3d272..590c0f9166 100644
--- a/test/config/test_system_config.rb
+++ b/test/config/test_system_config.rb
@@ -80,6 +80,7 @@ def parse_text(text)
       assert_nil(sc.enable_msgpack_time_support)
       assert(!sc.enable_jit)
       assert_nil(sc.log.path)
+      assert_nil(sc.maxstdio)
       assert_equal(:text, sc.log.format)
       assert_equal('%Y-%m-%d %H:%M:%S %z', sc.log.time_format)
     end
@@ -100,6 +101,7 @@ def parse_text(text)
       'enable_input_metrics' => ['enable_input_metrics', true],
       'enable_size_metrics' => ['enable_size_metrics', true],
       'enable_jit' => ['enable_jit', true],
+      'maxstdio' => ['maxstdio', 768],
     )
     test "accepts parameters" do |(k, v)|
       conf = parse_text(<<-EOS)
diff --git a/test/test_supervisor.rb b/test/test_supervisor.rb
index fd89ca8ce4..fa44ea39d9 100644
--- a/test/test_supervisor.rb
+++ b/test/test_supervisor.rb
@@ -1160,6 +1160,32 @@ def test_stop_parallel_old_supervisor_after_delay
     end
   end
 
+  data("Default", {})
+  data("Small", {maxstdio: 100})
+  data("Large", {maxstdio: 3000})
+  data("Very large", {maxstdio: 10000})
+  def test_maxstdio(cl_opt)
+    # TODO assert
+
+    omit "maxstdio is only for Windows" unless Fluent.windows?
+
+    supervisor = Fluent::Supervisor.new(cl_opt)
+    supervisor.setup_maxstdio
+
+    files = []
+    begin
+      10000.times do |i|
+        file = File.open(File.join(@tmp_dir, "#{i}.txt"), "w")
+        files.append(file)
+      end
+    ensure
+      puts files.length
+      files.each do |file|
+        file.close
+      end
+    end
+  end
+
   def create_debug_dummy_logger
     dl_opts = {}
     dl_opts[:log_level] = ServerEngine::DaemonLogger::DEBUG