The present invention is to provide a case comprising a structure for fastening a sliding button having a fixing member and a manipulating member together forming an L-shaped member, two spaced ribs provided on an inner surface of the manipulating member above the fixing member, and a projection provided on an outer surface of the manipulating member and adapted to insert through an opening of the case and project therefrom to outside of the case while placing the sliding button in the case; and a circuit board threadedly secured to a bottom of the case for clamping the fixing member and thus fastening the sliding button.