Vertical slot is a kind of fishways, and it can be analyzed in horizontally two-dimensional scheme. Numerical analysis of flow in vertical slot fishway is conducted by using a k-e turbulence model, and the flow pattern and velocity distribution in a compartment between vertical slots are obtained. The calculated results are compared with the experimental data to confirm the method of calculation. Systematic calculation based on the present model will provide a discussion on design for favorable geometry of fishways of vertical-slot type.