a circuitry is provided with a first switching contact . a first spacer is laminated on the circuitry so as to provide a first space above the first switching contact . a first , elastic sheet member is laminated on the first spacer and provided with a second switching contact opposing to the first switching contact in the first space . the first sheet member is operable to deform while using the first space to bring the second switching contact into an electrical contact with the first switching contact . a second spacer is laminated on the first sheet member so as to provide a second space above a first part of the first sheet member . a second sheet member is laminated on the second spacer , the second sheet member being operable to deform while using the second space to thereby deform the first part of the first sheet member . an elastic member is interposed between the first sheet member and the second sheet member at the second space . the elastic member has an elastic deformability which is higher than an elastic deformability of the first sheet member .