While there are contact joining and capacitance type switches for detecting an operation of a door handle, a problem that is to be solved by the invention is to solve problems of contact failure due to aging and a malfunction triggered by rain drops. According to the invention, a piezoelectric sensor (4) has such flexibility as to be annexed to a door handle (3), whereby a minute displacement of the door handle (3) can be detected with high sensitivity. Consequently, a sufficient signal output can be obtained only through a simple touch to the door handle (3), whereby a touch or contact to the door handle (3) can be detected. In addition, since electrodes are not exposed to the outside, the piezoelectric sensor (4) is made difficult to be affected by disturbance, and dust, rain, snow and the like which come to adhere thereto. Furthermore, since the piezoelectric sensor (4) can be deformed with suppleness, there are imposed few limiting conditions on a setting place and a space where to dispose the piezoelectric sensor (4) is diminished.