A knob section includes an elastic pawl protruding downward and contacting an outer surface of a light guide unit at an inner surface of the pawl. A holder includes a holding section contacting an outer surface of the elastic pawl. An illumination knob is provided by latching a recess of the elastic pawl to a protrusion of the holding section. The elastic pawl is sandwiched between an outer surface of the light guide unit and the holding section, thus allowing constituent components of the illumination knob to be held securely.