An equivalence verification unit (130) judges through equivalence verification, for each of corresponding combinations which are each a combination of a function included in pre-change source code and a function included in post-change source code, whether the functions included in the corresponding combination are equivalent to each other. A partial verification judgment unit (150) judges, for each of inequivalent ones of the corresponding combinations, whether the corresponding combination is a partial verification combination including a function where an inequivalent path, in which an inequivalent function is called, and a non-inequivalent path, in which a non-inequivalent function is called, are both included. A partial verification unit (160) judges, for each of the partial verification combinations, whether the functions included in the partial verification combination are partially equivalent to each other by excluding the inequivalent path and performing the equivalence verification.