The 5 working day's a week increase to fixed cost. Specially, the small ＆ medium size company more increase to manufacturing cost. The introduction of 5 working day's rule influence to labor cost in manufacturing cost. Also, it make disappear to fixed cost of 0.5 working day. Almost manufacturing company expect to have difficulty in product cost. The case of japan, many manufacturing company move to Asian countries after introduction of 5 working day's a week rule. The purpose of this study are the analysis of change product cost and suggest to solutions for a type of industries.