A structure is used to prevent an ultrasonic sensor from being damaged by a spring member provided for a bezel. A metal spring is fixed in a groove in a bezel. By setting depth of the groove to be larger than thickness of the metal spring, the metal spring is positioned on the inside further than an open end of the bezel. With the configuration, the metal spring is prevented from coming into direct contact with an ultrasonic transducer. Thus, a vibration face of the ultrasonic transducer is prevented from being damaged.