A door for attachment on the front of a machining tank of an electric discharge machine includes a door frame and first and second lifting doors that move up and down with respect to the door frame. When the first lifting door is lifted, pulleys attached on the first lifting door also move up, causing a belt wound around the pulleys and fixed to the door frame via a first belt-attaching member to rotate. As a result, the second lifting door, fixed to the belt via a second belt-attaching member, moves up with respect to the first lifting door.