To provide a power supply apparatus that can supply a large current and a small current to a load circuit in a switchable manner, with a minimum circuit scale and an efficient use of electronic devices and elements contained in conventionally used power supply apparatuses. The power supply apparatus 1 includes a power source 5 that supplies power to a load circuit 4 via one of a first path 2 and a second path 3, a switching unit 6 that switches between the first path 2 and the second path 3, a first switch 7 that controls a supply period that provides a reference for a first level of power supplied via the first path 2, a driver 10 including an open/close switch 8 that controls timing of opening and closing of the first switch 7, and a second switch 9 that controls a supply period that provides a reference for a second level of power supplied via the second path 3, wherein the first level of power is higher than the second level of power, the first path 2 runs through outside of the driver 10 while the second path 3 runs through inside of the driver, and the open/close switch 8 and the second switch 9 are a common element.