ULTRASONIC SENSOR

An ultrasonic sensor is provided with a sensor body, a cushion member, a retainer part and a waterproof seal. The sensor body has an ultrasonic microphone and a microphone support part. The cushion member covers a protrusion part of the ultrasonic microphone. The retainer part sandwiches a sandwiched part on a proximal end side between the retainer part and an outer peripheral surface of the ultrasonic microphone, while exposing an exposed part on a tip end side in the axial direction of the cushion member. The waterproof seal blocks a gap between a vehicle body component and the exposed part of the cushion member in an on-board state.