PURPOSE: To surely eliminate the occurrence of double registration of an item name by inspecting whether or not defined item names conform a common covenant on each defined item name and, at the same time, whether or not the item names conform a specific covenant.

CONSTITUTION: An item name inspection program 22 is stored in advance in an external storage device 2 and the program name is transferred to and described in a program name area 31. After a data item 41 is defined, the item 41 is inputted to a display screen 4 by operating an input section 5. A control section 1 sends the inputted data item 41 to a data item editing area 32 in a buffer memory 3 and makes an inspection following a common inspection program incorporated in the section 1. Then the section 1 checks the program name area 31 and executes the item name inspection program 22 after calling the program 22 from the external storage device 2. Therefore, double registration of an data item can be surely eliminated.