PURPOSE: To automatically find such timing information as setup time, hold time, etc., on a designed LSI.

CONSTITUTION: A circuit connecting characteristic information extracting device 1 extracts circuit connecting information A indicating the connecting relation in a circuit and circuit characteristic information B which is decided in connection with the size of each component of the circuit from the mask pattern P of an LSI. A circuit simulation input information preparing device 2 prepares circuit simulation input information D based on the information B and circuit parameter information C. The input information D contains a set of plural input signals having different timing and a circuit simulator device 3 simulates the set of output signals which is obtained when the set of plural input signals is inputted. A timing information computing device 4 obtains timing information F based on the set of the output signals.