The guide of design for the pool and weir type fishway, which has a lot of numbers of adoptions in weirs of our country, has been almost established. However, general-use forecast method of the flow in this type fishway, plunging flow or streaming flow, has not been established. It is necessary to develop the forecast method in order to achieve a more appropriate design, because the difference of such a flow influences the upstream migrating behavior of the fish. In this research, it is clarified that the simulated results by the numerical analysis method, using the VOF method in generalized curvilinear coordinate and the standard κ-ε model to which the modified LK model and the Durbin model are applied, are in good agreement with experimental measurements using a full-size hydraulic model of a various shape. This method will be general-use forecast method of the flow in this type fishway for actual design.