To determine a contradiction between requirements and specifications in a specification document for system/software development without labor for preparation in advance, provided is a requirements contradiction detection system, including: a relevancy detection part for detecting, for two requirements expressed in texts, a relevancy between the two requirements based on a similarity between one requirement acquired by converting one of the texts based on a predetermined contradiction rule and another requirement that is not converted; and a contradiction detection part for detecting whether or not the two requirements contradict each other based on a detection result of the relevancy detection part, the similarity calculated by the relevancy detection part, and a similarity between the two original requirements before conversion.
