Abstract The competition between the superconductivity and the itinerant ferromagnetism and the direction of the successive phase transition are investigated by using a single-band model and the mean-field approximation. Taking into consideration the fact that the effective attraction and Coulomb repulsion exist in different energy regions, we calculate the free energy and the ferromagnetic and superconducting order parameters of the system considering that the effective attraction and Coulomb repulsion exist in the different energy regions. As a result, we show that only the successive phase transition (para normal → ferromagnetic → superconducting state on cooling) is possible for an itinerant system and that the successive phase transition (para normal → superconducting → ferromagnetic state) will never occur. This is in agreement with the experimental results for Y 9Co 7. Therefore, a more reasonable mean-field theory of the itinerant magnetic superconductor is provided in this article.