A switching power supply that has a reduced conduction loss, when a direct current power supply is connected as an input power supply, by changing a part of a circuit for alternating current-to-direct current conversion, is provided. The switching power supply includes power input terminals to which the direct current power supply or an alternating current power supply is connected; power output terminals configured to output electric power; a smoothing capacitor connected between the power output terminals; a first non-insulated chopper circuit connected between the power output terminals; a second non-insulated chopper circuit connected between the power output terminals; and a switching circuit configured to switch a connection circuit provided between the first non-insulated chopper circuit and the second non-insulated chopper circuit, and the power input terminals.