1. A library creating apparatus, comprising: a recognizing unit which recognizes a simulation object circuit in circuitry by searching downstream for a specific circuit, evaluating whether the specific circuit is a flip-flop and recognizing a circuit ranging from an input end of the circuitry to the specific circuit as the simulation object circuit to be simulated; a simulation unit which simulates the simulation object circuit recognized by said recognizing unit; and a creating unit which creates a library of characteristic values of the simulation object circuit based on a simulation result obtained by said simulation unit.