A resin window includes a plate-shaped main body portion and a gear projection portion that is molded integrally with the main body portion so as to project in a thickness direction of the main body portion from a rear end portion of the main body portion. A part of a side face of the gear projection portion is surrounded by a gear-side guide frame for guiding the raising/lowering of the resin window. The gear projection portion includes a meshing gear provided along a vertical direction to mesh with a drive gear, and positioning members provided respectively on upper and lower end portions of the gear projection portion to abut on an inside surface of the gear-side guide frame. When the drive gear is rotated, the positioning members slide relative to the inside surface of the gear-side guide frame, and thus the resin window can be raised or lowered along the gear-side guide frame.