PURPOSE: To eliminate the influence of external light and to improve the reliability of a sensor element in an IR sensor consisting of a pyroelectric type element photodetecting part, reflecting film, built-in active element, etc. by covering the built-in active element with a visible light shielding film.

CONSTITUTION: A supporting frame 3 is provided to the center of a stem 1 and the pyroelectric type element 4 is provided thereon. The photodetecting part 5 consisting of a metallic film is provided on the element 4 and a reflecting film is provided to the rear to increase the temp. of the photodetecting part. The built-in active element 10 formed on an output resistor 8, resistance element 9, etc. is provided and is electrically connected to the element 4. The element 10 is coated with the visible light shielding film 16 except the photodetecting part 5. Since the visible light shielding film is provided to said element, the reliability of the pyroelectric type IR sensor element is improved by eliminating the influence of the external light. The exact measurement of temp. is made possible without being affected by lighting in a housing when the element is used for a microwave oven for cooking.