To provide an optical sensor that can ensure accuracy of positions of a light projecting unit and a light receiving unit in a case. The optical sensor includes a case, an integrated light projecting module that includes a light emitting unit and a light projecting lens, a light receiving unit configured to receive reflected light of light projected from the light projecting module, and a light receiving lens unit configured to form an image of the reflected light on the light receiving unit. The light projecting module, the light receiving unit, and the light receiving lens unit are each independently and directly fixed to the case.