<p>A pyroelectric SR-sensor in which a pyroelectric light receiving element (2) is mounted on a MID substrate (5) or a ceramic substrate (25) of which thermal conductivity is less than 0.02 cal/cm.sec. DEG C in a manner that the both end portions of the pyroelectric light receiving element are supported by the substrate with the central portion of the pyroelectric light receiving element being spaced from the substrate, and chip parts (6, 7) are further mounted on the substrate.</p>
