An electrode 4 for detecting a biological signal and a loop antenna 3 are integrally mounted on a support 2 placed on the surface of a living body and a transmitter 5 is placed on the support 2. A biological signal detected on the electrode 4 is input through a connector 11 to electric circuitry 10 of the transmitter 5 and an electric signal processed by the electric circuitry 10 is output through connectors 12 and 13 to both ends of the loop antenna 3 from which the biological signal is emitted to a receiver. At this time, the opening face of the loop antenna 3 is in a direction almost perpendicular to the surface of a living body for improving sensitivity.