While the effectiveness of a model inspection method as a means for detecting software defects is known, large-scale software cannot be handled due to great amounts of calculation required for inspection. According to the present invention, after a model inspection problem of software is attributed to be a satisfiability determination problem, the problem is converted to a type that can be solved by a solver used for solving a notification optimization problem having constrained conditions, and the satisfiability is determined in a numerically analytical manner.