To ensure an accurate timing analysis by not applying a uniform delay factor but applying a delay factor depending on characteristics of each clock path, to branch clock lines.

With an input of a net list 101, a path-specific delay factor setting step 104 sets a maximum value and minimum value of a delay factor depending on characteristics of each path, in clock paths of a data sending FF and data receiving FF. A timing analysis step 106 uses the net list 101, a constraint file 102, a delay information file 103 and a path-specific delay factor file 105 set in the path-specific delay factor setting step 104 to execute a setup check and a hold check and thereby a timing analysis depending on path characteristics.