Recent software system contain many functions to provide various services. According to this tendency, it is difficult to ensure software quality and to eliminate crucial faults by conventional software testing methods. So taking the effect of test engineer’s skill on test item generation into consideration, we propose a new test item generation method,which supports the generation of test items for illegal behavior of the system. The proposed method can generate test items based on use-case analysis, deviation analysis for legal behavior, and faults tree analysis for system fault situations. From the results of the experimental applications of our method, we confirmed that test items for illegal behavior of a system were effectively generated, and also the proposed method could effectively assist test item generation by an engineer with low-level skill.