To obtain a PLC input-output database system in which the design efficiency of an S/W design task of a PLC is improved by unitarily managing an H/W configuration and data of an S/W programming and making double management and an overlapping input unnecessary.

This data system is provided with a database 10 including equipment information 11 of a device to be managed and input-output information 12, a PLC programming function 41 for performing PLC programming of the equipment information 11 and the input-output information 12 from the database 10 to acquire them in various lists, and a system definition editing function 14 for unitarily managing the equipment information 11 and the input- output information 12.