PURPOSE: To provide quickness of stopping a high frequency generating source at the time of abnormality so as to improve safety of a device by providing a temperature detector in a position where easily cooled so that a setting temperature for actuating the high frequency generating source can be set lower.

CONSTITUTION: A cooling air guide 10, integrally provided with a magnetron 1, is arranged so as to guide cooling air from a propeller fan 3 branched to the magnetron 1 and a high voltage transformer 2. A temperature detector 14 is mounted to a position in an external surface side below the guide 10 and further provided with an air guide opening 11. This detector 4, on the one hand being provided in the guide 10 integrally formed with the magnetron 1, detects a high temperature by heat transmission from the magnetron 1 when the fan 3 is stopped in the case of generating abnormality, and the detector 4, on the other hand being cooled by the cooling air from the fan 3, detects a low temperature when the fan 3 is normally actuated. In this way, safety of a device can be improved by stopping the magnetron 1 in a safe condition not generating a very high temperature.