A semiconductor integrated circuit apparatus includes a first controlled circuit having at least one MOS transistor and a substrate bias control unit for generating a substrate bias voltage of the MOS transistor, wherein when the substrate bias control unit is set in a first mode, a comparatively large current is allowed to flow between the source and drain of the MOS transistor, while when the substrate bias control unit is set in a second mode, the comparatively large current allowed to flow between the source and drain of the MOS transistor is controlled to a current of smaller value. The value of the substrate bias applied to the first controlled circuit is larger in the second mode than in the first mode for the substrate bias of the PMOS transistor, and smaller in the second mode than in the first mode for the substrate bias of the NMOS transistor. The power supply voltage applied to the first controlled circuit is controlled to a smaller value in the second mode than in the first mode.