In one aspect of the present invention, data to be written is divided into a plurality of pieces of divided data of a maximum size or less to calculate an offset of each piece of divided data, a frame issuing an instruction to a PLC to write a predetermined terminal code in a head address of a data area is transmitted, a frame issuing an instruction to the PLC to write the divided data at a position of the corresponding offset from the head address of the data area with respect to the divided data except a head divided data is transmitted, and a frame issuing an instruction to the PLC to write the head divided data in the head address of the data area is transmitted.