To reduce cost by sharing a communication device for a safety device and a controller.

A data separator is provided among a communication device, controller and safety device. The communication data separator is equipped with a receiving buffer which registers communication data acquired from each device; a priority managing table which stores a dependence value where each bit corresponds to that at a transfer destination of communication data and a priority value which is determined by the kind of data; a processing order list which stores the order of transfer processing; a priority register means which determines the dependence value and the priority value of communication data acquired from the receiving buffer with reference to the priority managing table, and determines the order of transfer processing of the communication data acquired from the receiving buffer and registers it in the processing order list by using the dependence value and the priority value of the communication data and the dependence value and the priority value of the communication data registered in the processing order list; and a communication data transfer means which executes the transfer processing of the communication data, according to the order registered in the processing order list.