An ultrasonic flowmeter capable of increasing the amplitude of, and the receiving sensitivity for, an excited signal is provided. The ultrasonic flowmeter according to the present invention includes two or more ultrasonic transducers on a transmission side and two or more ultrasonic transducers on a receiving side, located as being away from each other on an outer surface of a tube having a fluid flowing therein. The two or more ultrasonic transducers located on the transmission side are driven so as to press the tube at substantially the same pressure to increase an amplitude of an ultrasonic wave. The ultrasonic flowmeter according to the present invention includes adjustment members converting an ultrasonic signal into an ultrasonic signal suitable to measurement between the tube and the ultrasonic transducers. The adjustment members each have a curved surface or a groove at a surface thereof contacting the tube.