Computer simulation of the magnetizing process has been carried out by applying a numerical model to the theory of the rotation magnetization for magnetic materials, This model has been made in order to adjust to the two-dimensional magnetic property. This numerical model is combined with the finite element method in which the magnetic scalar potential and the magnetization are regarded as unknown quantities. It is possible to calculate that the magnetic materials with single domain structure are magnetized in the mode of rotation or of reverse of the magnetization vector.