Abstract: An optical measuring head which includes a cylindrical portion having a circular cross section, a plurality of light projecting fibers axially disposed in the cylindrical portion through a predetermined distance, a light receiving fiber provided along an axis of the cylindrical portion, and a convex lens formed, at its outer peripheral portion, with a light receiving face for receiving the light from the light projecting fibers and directing the light through the lens so that the light will be incident upon a flat surface of the lens adjacent an object to be measured, through an angle smaller than a critical angle whereby the light will not be reflected by the flat surface, and disposed at a position coaxial with the light receiving fiber for focusing on a forward end face of the light receiving fiber.