To provide a power supply system that makes it possible to improve power factor and power loss more than conventional and reduce the size of a transformer.

The power supply system 100 includes: a power supply transformer 110 that converts 100 V AC into 24 V AC; and multiple power supply units 200-1 to 200-n connected to the power supply transformer 110. The power supply unit 200-1 includes: a rectifier circuit 210 that rectifies 24 V AC by a synchronous rectifier bridge; a power factor improvement circuit 220 that improves the power factor of rectified voltage; and an output circuit 230 that outputs direct-current voltage. The power factor improvement circuit 220 includes an inductor L, FET 1, FET 2, and a control circuit 222 that controls switching of the FET 1 and the FET 2. The control circuit 222 adjusts the duty ratios of the FET 1 and the FET 2 and causes the output circuit 230 to output a desired direct-current voltage.