A projection lens unit includes a magnifying optical system is provided. A second magnifying lens barrel has a shape of double circular cylinders, and a first magnifying lens barrel is fitted to an outer circular cylinder. Further, a second magnifying lens is in contact with and fixed to a step portion of inner circular cylinder. In a manufacturing step thereof, the second magnifying lens is inserted into the inner circular cylinder of the second magnifying lens barrel to be into contact with the step portion. A front end portion of the inner circular cylinder is plastically deformed by being heated and pressed to fix the second magnifying lens. An outer peripheral edge of the front end portion has a curved surface. The curved surface of the front end portion is made to be smaller in radius of curvature than the second magnifying lens.