An exposure apparatus which can change a reticle efficiently with a simple arrangement is provided. A hub assembly, hub gear box and input gear box are mounted to an independently pivoting swing arm. Lateral face regions of the optical element, the regions extending from the cover surface in the direction of the corners of the base, are formed by flat or rotationally symmetrical surface regions. A plurality of vent holes through the wall communicates with the interior space to vent combustion gases. The control unit executes control so as to raise the discharge tray in response to the determination that the lowering of the discharge tray has been disabled. The battery tray is slidably mounted to the battery tray support structure for movement between a first operational position and a second maintenance position.