A projector to which a ceiling suspension attachment is fixed. The projector accommodates an internal device. The projector is provided with an outer case including a bottom wall that defines an outer bottom surface and an inner bottom surface of the outer case. Insert nuts are arranged on the bottom wall. Each insert nut includes a threaded hole to which a first coupling screw is fastened and a second coupling screw can be fastened. The first coupling screw couples the attachment to the outer bottom surface of the bottom wall, and the second coupling screw is fastened to the threaded hole from a side opposite to the first coupling screw. The second coupling screw is fastened at least one of the insert nuts to couple the inner device to the inner bottom surface of the bottom wall.