Usually hydrodynamic pressures on a restrained ship in waves can be obtained by the Ordinary Strip Method (O. S. M.) using Watanabe's approximation, namely the pressures are obtained from multiplying the radiation potential by the orbital velocity at the mean draft. However, these solutions are not exact, since the boundary condition on the surface is not satisfied precisely. In this report the solutions which satisfy the boundary condition on the surface of the ship exactly (this method is named Strict Strip Method, S. S. M.) are presented, and the results of calculation in the case of zero forward speed are compared with those by O. S. M. and the experimental results. It is shown that the agreement between the calculation and measured values is good on the weather side in both methods, but on the lee side, the theoretical predictions by S. S. M. show a more satisfactory coincidence with the measured values than those by O. S. M.