PURPOSE: To provide a superconducting electromagnetic wave sensor having excellent sensor characteristics in which the sensor can be cooled sufficiently.

CONSTITUTION: A signal transmitting means for connecting a superconducting electromagnetic wave sensor 3 mounted on a cold head 2 placed in a thermally insulated vacuum vessel 1 electrically with terminals 17, 18, 19 disposed on the vessel 1 is constituted through magnetic coupling means 7, 8, 9 comprising second coils 7b, 8b, 9b disposed oppositely to first coils 7a, 8a, 9a with coil faces thereof being spaced apart from each other. This constitution reduces heat flowing into the superconducting electromagnetic wave sensor 3 from the outside of the thermally insulated vacuum vessel 1.