To provide a protective device mainly used in protecting an electric motor of a closed type motor-driven compressor and having a means for heightening strength of an electrical insulation film or the like.

In this protective device 1, a thermally actuated switch 2 is covered with an electric insulating coating 3. Lead wires 4A, 4B are connected to the thermally actuated switch 2, and a connecting part projected from a switch case is covered with an electric insulating cover 5. The cover 5 has the side extended from the switch end part and shaped like a comparatively wide plane. Thus, the projecting part of the thermally actuated switch 2 is covered with the coating, whereby the projecting part can be prevented from directly abutting on the insulating coating, so that breakage of the insulating coating due to stress concentration in handling and fitting the protective device for the electric motor. The cover has a comparatively wider plane extended from the thermally actuated switch end part, whereby in fitting the protective device, a stable fitting attitude can be taken with reference to the plane.