An ultrasonic flowmeter includes a main body that calculates components parallel to a pipe axis regarding the velocity of fluid on the basis of a first propagation time difference, which is the difference in time between the time that ultrasonic waves transmitted from a second ultrasonic transceiver and the time that ultrasonic waves transmitted from a first ultrasonic transceiver propagate through a first flow propagation path traversing inside the pipe in the radial direction for 2n−1 times (n is a positive integer), and a second propagation time difference, which is the difference in time between the time that ultrasonic waves transmitted from the second ultrasonic transceiver and the time that ultrasonic waves transmitted from the first ultrasonic transceiver propagate through the second flow propagation path traversing inside the pipe in the radial direction for 2m−1 times (m is a positive integer other than n).
