PURPOSE: To perform a delay simulation which is closer to the operation of an actual device by calculating a wiring delay for which on and off states of a transfer gate are considered.

CONSTITUTION: Input data and input patterns are fetched and a gate output terminal extracting means 103 extracts a gate output terminal based on the converted internal data. Then, a connection relation retrieving means 104 retrieves a connection relation, while considering whether a transfer gate in connected or not for the extracted terminal. A delay calculating means 105 calculates the delay by classifying into a case where the transfer gate is connected and a case where it is not connected by using the retrieval result. Thus, a simulation is executed based on the prepared internal data and the result is preserved. Thus, since the delay time can be calculated by considering the on/off of the transfer gate, an error can be reduced.