An operation timing verifying apparatus and program for accurately verifying operation timings of a semiconductor integrated circuit in design with suppressing design time and cost. The operation timing verifying apparatus and program sets an unreal corner condition that all delay elements present a maximum delay as an operating condition, performs operation timing analysis in the operating condition, thereby extracting an operation-violating circuit path, if any, from a circuit layout, sets a real corner condition that at least one element type of delay elements from among the delay elements present a maximum delay as the operating condition and performs the operation timing analysis on only the operation-violating circuit path to determine again whether an operation violation exists therein.