NOVELTY - A transmission-type photoelectric sensor comprises a plastic element holder including a light path extending from the aperture of the base wall to the lens; and an intermediate light-blocking wall extending in an equally spaced level from the base wall and the lens to limit the spread angle of light. The element holder is a single-piece molded product including the intermediate light-blocking wall.    USE - As transmission-type photoelectric sensor.    ADVANTAGE - The invention provides an element holder unit that can be molded as a single-piece product including a light-blocking wall for limiting the spread of light. The photoelectric sensor of the invention is free from assembling errors. It has reduced assembling steps.    DETAILED DESCRIPTION - A transmission-type photoelectric sensor comprises an optical element (5); a plastic element holder having a base wall which has an aperture (4) and detachably contacts the optical element; and a lens (6) positioned adjacent to the element holder opposite from the base wall. The element holder includes a light path extending from the aperture of the base wall to the lens; and an intermediate light-blocking wall (7) extending in an equally spaced level from the base wall and the lens to limit the spread angle of light. The element holder is a single-piece molded product including the intermediate light-blocking wall. An INDEPENDENT CLAIM is also included for a method of manufacturing a plastic element holder to be assembled in a transmission-type photoelectric sensor by simultaneously setting a first die for making a lens-side half of the light path from the lens to the intermediate light-blocking wall and movable in parallel to the optical axis and a second die for an element-side half of the light path from the base wall to the intermediate light-blocking wall and movable across the optical axis; and injecting a material into a mold to make the lens-side half of the light path, the intermediate light-blocking wall and the element-side half of the light path.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of an emitter holder unit having element holders spaced in equal intervals.    Aperture (4)    Optical element (5)    Lens (6)    Light-blocking wall (7)    Through hole (8)    Sidewall (9)    Light-emitting surface or light-receiving surface (21)    Substrate (29)    Lens unit (50)