PURPOSE: To simplify an operation by an operator by optionally and easily specifying and altering command data corresponding to various commands during the operation of a CAD system and also easily switching commands.

CONSTITUTION: A display control part 13 controls a command display control part 11 according to selective information on a command imparted from a command input processing part 12 and makes information displayed on a command data panel correspond to a currently selected command. A standard CDP consisting of a standard information group which is common to many commands and a custom CDP consisting of information groups characteristic to specific commands are prepared as a command data panel. The custom CDP is prepared for plural specific commands and information groups suitable for them are displayed.