Although formal methods seem to be useful, these is no clear way for beginners to know whether the methods are suit for them and for their problem domain, before using the methods in practice. We propose a method to confirm the suitability of a formal method. The method is realized as a pilot course based on the PSP. A course mentioned in this paper is designed for a typical formal method, VDM. Our course also helps beginners of VDM to learn VDM gradually and naturally. During the course, they can confirm its suitability as follows; First, they practice several exercises for software development, while techniques of VDM are introduced gradually. Second, process data and product data of software development are recorded in each exercise. Third, by evaluating these data by several metrics, they can confirm the suitability of VDM for their work.