A support plate can be disposed close to a display screen without having to provide a latching mechanism to the support plate, a push button device can be easily attached and detached, and the fixing of the push button device can be carried out simultaneously with the locking of the flexible wiring. There are provided a push button device that is inserted into an opening in a transparent plate 50 from the front side, and an annular lock plate that is disposed on the back side of the transparent plate and is fitted to the outer peripheral portion of the bottom part of the push button device from the back side. The outer peripheral portion of the bottom part of the push button device and the inner peripheral portion of the lock plate have snap-fit structures that are fixed to the outer peripheral portion of the bottom part by rotating the lock plate. The lock plate is configured to have a diameter larger than that of the opening and so as to abut the transparent plate in a fixed state, and furthermore, a reinforcing portion of the flexible wiring is sandwiched and pressed by the end surfaces on the flange portion side of a connection opening.