A lens member includes a central axis, a light-incident side including a Fresnel-lens surface provided with a plurality of annular prisms concentrically arranged with respect to the central axis, and a light-exit surface opposite to the light-incident side. The Fresnel-lens surface further includes an annular lens portion that is concentrically arranged with respect to the central axis and that is extended to be longer and wider than the plurality of annular prisms. Provided is an optical unit in which a light source and a lens member are combined, and parts are disposed in a space provided in an outer periphery of the annular lens portion.