To effectively monitor a device and monitor a process by referring to an equipment table and an icon list and displaying a device mark along with a device name together with the information display of the device.

The device name, a form name, an address and an icon NO, etc., for respective equipments are entered to the equipment table and the correspondence of an icon number and the device mark is entered to the icon list. A work station 1 displays a present state in the respective kinds of forms for the respective equipments connected to a field bus 7 and the device name, the device mark and the present state are displayed for the respective devices. For instance, the equipment table is referred to, and when the icon NO of a certain device is '1', the bit map of the NO 1 of the icon list is selected and displayed. Also, when the address of the device is 0×01 by referring to the equipment table, a communication program 1b is executed, the state of the device of the address 0×01 is read and the state is displayed.