Abstract: In a switching power supply apparatus for performing a switching control of a power MOS transistor that flows current to a coil and converting input voltage into output voltage, even if there occurs offset voltage in a current sensing operational amplifier, source potential of a current sensing MOS transistor is precisely kept at source potential of a low side power MOS transistor. For example, an offset cancel capacitor is arranged at an inverting input terminal of the current sensing operational amplifier, and voltage in the direction to offset the offset voltage occurring in the operational amplifier is charged to this capacitor.