PURPOSE: To improve detection precision and facilitate production, by connecting two detecting elements of the same material having the pyroelectric effect so that they may have polarities opposite to each other.

CONSTITUTION: Step part 13 is provided in one side of metal ring-form support stand 12 to reduce the outside diameter. Pyroelectric element 10 is caused to adhere to the part between step parts 13 of metal ring 12, thus obtaining the unit of a thin film infrared ray detecting element. These units 900 and 902 are superposed in the direction orthogonal to the infrared incident light and are connected through reflective plate 901 so that polarities for the pyroelectric effect may be opposite to each other. In this case, unit 900 becomes the essential infrared detector. By the lamination effect with the opposite polarity, not only temperature compensation is obtained but also the noise voltage vibration, noise, shock, and so on generated by the piezoelectric characteristic of these elements is cancelled.