An ultrasonic sensor (10) includes a transmission and reception unit (11) for transmitting and receiving an ultrasonic wave, a holder (12) and an attachment (13) for fixing the transmission and reception unit (11) to the bumper (1) of a vehicle, and light source units (14a, 14b) mounted in a back side of the bumper (1). The holder (12) is shaped so as to be exposed on a surface of the bumper (1), and guides light beams emitted by the light source units (14a, 14b) to the surface of the bumper (1), to project the light beams from a light projecting surface (12a) to the outside of the vehicle.