PURPOSE: To calculate a delay time on which mount information is reflected speedily and accurately.

CONSTITUTION: A network storage means 1 is stored with network information on a circuit. A floor plan storage means 2 is stored with the floor plan of the circuit as position information on components of the circuit. A wiring length calculating means 3 finds the expected wiring length of the network from the information on the floor plan and network. A wiring length storage means 4 is stored with the expected wiring length. A wiring delay time calculating means 5 calculates the wiring delay time from the expected wiring length. A wiring delay time storage means 6 is stored with the calculated wiring delay time.