A power source cut-off system enabling the user to cut off power supply from an outlet even when user is out comprises an outlet tap for supplying power to an electric apparatus by connecting it to a home commercial power source and a telephone set for controlling this outlet tap and connected to an external telephone line. The outlet tap comprises an outlet to which the electric apparatus is connected, a power cut-off means for cutting off the power source at this outlet, a reception means for receiving a radio signal transmitted from the external telephone set, and a control means for cutting off the power source at the outlet by the power source cut-off device according to the radio signal received by this reception means. The telephone set comprises a control signal reception means for receiving a control signal transmitted via an external communication apparatus, and a transmission means for transmitting a radio signal to the outlet tap on the basis of the control receiving means.