To use the same item for both reading and writing data by converting the item designated by the operator into a module number and an in-module relative address so as to designate a module in a sequencer thereby eliminating the need for registration of separate items.

When the operator selects an operation menu 11 from a setting menu for write processing, the operation menu 11 issues a data write request to a data write section 12. Thus, the data write section 12 uses an entered item name for a key to reference a sequencer item table 13 and to obtain a module number of a corresponding module and a relative address in the module. Then the data write section 12 writes writing data by using the module number and the relative address. The data are written by using a message communication function of a control LAN that designates the address of a transmission destination to transmit the data.