PURPOSE: To provide an optical sensor which ensures moisture resistance, resistance to drop and vibration proof of an optical part, moreover, provides a better temperature characteristic and also achieve the production thereof with a high mass productivity at a low cost.

CONSTITUTION: This optical applied sensor has a plurality of optical parts containing at least lenses 23 and 27, a polarizer 24, an analyzer 26, an optical element 25 and optical fibers 21 and 29 and measures light optically as working on the optical element 25 by transmitting the light via the optical parts. The optical parts are put closely without clearance through a synthetic resin 30 while being molded by the synthetic resin 30 in the perimeter thereof.