An ultrasonic flowmeter includes: an emission trigger oscillator outputting a trigger signal; an ultrasonic oscillator generating and outputting ultrasonic pulses by the trigger signal from the emission trigger oscillator; an ultrasonic pulse receiver transmitting the ultrasonic pulses output from the ultrasonic oscillator toward a measurement line within a fluid, and receiving an ultrasonic echo signal serving as reflected waves reflected off an ultrasonic reflector suspended within the fluid; a signal processor subjecting the ultrasonic echo signal received by the ultrasonic pulse receiver to signal processing; and a signal analyzer analyzing the ultrasonic echo signal subjected to the signal processing by the signal processor, calculating the position and speed of the ultrasonic reflector positioned along the measurement line, and measuring at least one of the flow-speed distribution and flow of the fluid from the calculated results.