diff --git a/lib/procon_bypass_man/device_connection/executor.rb b/lib/procon_bypass_man/device_connection/executor.rb
index 056a221c..3e656a51 100644
--- a/lib/procon_bypass_man/device_connection/executor.rb
+++ b/lib/procon_bypass_man/device_connection/executor.rb
@@ -115,7 +115,8 @@ def drain_all
     ProconBypassMan.logger.error "timeoutになりました(#{e.message})"
     procon.write_nonblock('8006')
     5.times do
-      procon.read_nonblock(64)
+      data = procon.read_nonblock(64)
+      ProconBypassMan.logger.info "(>>> #{data.unpack("H*")})"
     rescue IO::EAGAINWaitReadable
     end
     compressed_buffer_text = ProconBypassMan::CompressArray.new(debug_log_buffer).compress.join("\n")