To surely transfer data between a controller and control equipment without limiting the number of mounting of option modules.

When a synchronizing signal is inputted, an option module stores the data of a PLC module, and when the synchronizing signal is inputted, the option module calculates data to be outputted to the control equipment, and outputs the data to the control equipment in each update cycle. The PLC module holds a stand-by status without executing a user program until the data of the PLC module are fetched by the option module, and the PLC module executes the user program according to a data storage completion signal from the option module, and synchronizes the PLC module and the option module.