The ultrasonic flowmeter includes: a pair of ultrasonic oscillators; a measurement section for measuring a time in which an ultrasonic wave propagates between the pair of ultrasonic oscillator; and a calculation section for calculating the flow of the fluid flowing in a flow measurement cross section based on an output from the measurement section. The flow measurement section and the pair of ultrasonic oscillators are configured so that an influence of a reflected wave reflected from a wall of the flow measurement section on a measurement result is reduced.
