A PoE power supply system includes a cable, a power supply device, a power reception device, and a request switch. The power supply device includes a power supply block and a power supply control block. The power supply block is configured to enable a connection state between the power supply device and the cable to be switched. The connection state includes a power supply state in which the power supply device is supplied with power required for operating the power supply device via the cable, and a standby state in which the power supply request signal is receivable by the power supply device via the cable. The power supply control block is configured to switch the connection state to the power supply state in response to receiving a power supply request signal output from the request switch and requesting the power supply device to resume supplying the power.