Abstract: In an ultrasonic flow meter for measuring the flow rate of a fluid flowing through a pipe by determining the frequency difference between ultrasonic waves traveling within the fluid in the direction of flow of the fluid and in a direction opposite thereto, respectively. Each of the ultrasonic transmitters and receivers is connected to the pipe through an individual guide rod having disposed on its outer surface ridges which are adapted to cause ultrasonic waves reflected from the ridged surface to conceal one another out, and a thin gold sheet interposed between the guide rod and the pipe.