A finite-difference method for solving the time-dependent three-dimensional laminar flows is proposed, with the aim of reducing the computer time. The method is a p-u method (p : pressure, u : velocity) using a convective-difference scheme, and the accuracy is increased by applying the predictor-corrector method. The solutions satisfy sufficiently the condition of continuity throughout the flow region. The method is suitable to the strongly time-dependent flow problems. In the numerical examples, it is shown that the computer time by the present method can be saved as compared with the existing method.