Abstract: A thermopile type detector which is constituted by an electrically insulating film, a thermopile supported on the film, a semiconductor substrate supporting the film, and a temperature sensing element on the surface of the substrate on which the film is supported and in the neighborhood of a cold junction of the thermopile. The temperature on the substrate immediately adjacent a cold junction of the thermopile can be measured for use in compensating the output of the thermopile for the changes in temperature of the cold junction. The temperature sensing element can be a semiconductor material such as a diode or a transistor forming a semiconductor with the substrate.