In order to solve the noise problem occurring in a switching power supply, provided is a power supply device having: a plurality of switching power supplies (POW1-n) that receive supply of electric power from a common primary side power supply (Vin); and a control unit (140) for controlling operations of the switching power supplies (POW1-n). The control unit (140) inputs control signals (St1-n) to the respective switching power supplies (POW1-n), the control signals (St1-n) indicating the timings of turning on switching elements. The switching power supplies (POW1-n) turn on the switching elements at timings in accordance with the control signals (St1-n) and draw current from the primary side power supply (Vin). A first control signal (St1) input to a first switching power supply (POW1) and a second control signal (St2) input to a second switching power supply (POW2) are adjusted so that the switching element of the first switching power supply (POW1) and the switching element of the second switching power supply (POW2) are not switched from OFF to ON at same timing.