PURPOSE: To prevent an adhesive from adhering to the corner part of a molding without fail and thereby improve the reliability of bonding in a thermal shock test.

CONSTITUTION: A base plate 7 of a light detector is bonded by the potting method to near a recessed corner part of a frame 1 provided with a groove 1a in the corner part. Since an adhesive used in the above bonding has a relatively high viscosity, the groove 1A, together with the surface tension of the adhesive, prevents the adhesive from reaching the corner part. Thus the occurrence of stress due to adhesion of the adhesive to the corner part is prevented, preventing separation in the thermal shock test.