Light from a light source enters a first small diameter fiber at an incident angle of 0°. Exit light from the first small diameter fiber has a substantially convex light intensity distribution in a diameter direction. Light from a light source enters a second small diameter fiber at an incident angle of 12°. Exit light from the second small diameter fiber has a substantially concave light intensity distribution in a diameter direction. The exit light from the first and second small diameter fibers enters a large diameter fiber via a fiber connector. Light inside the large diameter fiber has a substantially uniform light intensity distribution in a diameter direction with a light intensity not less than a predetermined value. The light is radiated as illumination light from a light exit section of the large diameter fiber.
