PURPOSE: To supply power from a power supply unit in common to a facsimile main body and a-portable telephone set by connecting the facsimile main body and the portable telephone set via a portable telephone adaptor.

CONSTITUTION: A portable telephone set 3 consists of a telephone main body 9 and a telephone battery 10. The telephone battery 10 sends power to the telephone main body 9. The portable telephone set 3 is connected to a connector 8 of the facsimile main body 1 via the portable telephone adaptor 11. A power switch 6 of the facsimile main body 1 is closed to supply power from a power supply unit 2 to a DC/DC converter 5 to implement facsimile communication, then the portable telephone adaptor 11 is connected between the connector 8 of the facsimile main body 1 and the portable telephone set 3 in place of the telephone battery 10 and power is supplied from the power supply unit 2 with a large capacity to the telephone set main body 9 of the portable telephone set 3 through the connection.