Abstract: An ultrasonic flow rate measuring device which measures a flow rate of a medium flowing in the tube body, when one of a plurality of the ultrasonic transmitting-receiving means transmit an ultrasonic wave as a transmitting means, by making another one of a plurality of the ultrasonic transmitting-receiving means receive the ultrasonic wave as a receiving means, and when the other ultrasonic transmitting-receiving means transmit the ultrasonic wave as the transmitting means, by making the one ultrasonic transmitting-receiving means receive the ultrasonic wave as the receiving means, wherein an ultrasonic wave propagation control means which controls a propagation of the ultrasonic wave is equipped between the ultrasonic transmitting-receiving means as the transmitting means and the receiving means. Further, the ultrasonic flow rate measuring device is easily mounted to a tube body.