A power supply circuit comprises a power transistor, a differential amplifier, an I/V converter circuit, and an inverting amplifier, wherein the differential amplifier comprises a first current path in which a first resistor element, a first current mirror transistor, and a first control transistor are connected in series, and a second current path in which a second resistor element, a second current mirror transistor, and a second control transistor are connected in series, and the power supply circuit comprises a phase compensating capacitor element connected in parallel with the inverting amplifier, and a ripple removal rate improving capacitor element which is connected between ground and a connection point between the first resistor element and the first current mirror transistor, or between the ground and a connection point between the second resistor element and the second current mirror transistor.