Abstract: An ultrasonic flowmeter includes two ultrasonic transceivers. Each of the ultrasonic transceivers includes a cylindrical transmitting body closely fixed to the outer peripheral surface of a measurement pipe through a fluid flows so as to surround the measurement pipe, and an ultrasonic transducer surrounding the measurement pipe and spaced apart from the outer peripheral surface of the measurement pipe. The transmitting body is made of a rubber material and has axial end surfaces extending perpendicular to the axis of the measurement pipe. The axial end surface of the ultrasonic transducer is fixedly secured to the axial end surface of the transmitting body, and the ultrasonic transducer is extended and contracted in the axial direction thereof by applying a voltage between the axial end surfaces of the ultrasonic transducer.