An ultrasonic flowmeter includes a plurality of ultrasonic wave elements attached to an outer wall of a pipeline through which a measurement target fluid flows, and configured to transmit and receive an ultrasonic signal, wherein at least one of the ultrasonic wave elements is an ultrasonic wave transmission element and is attached to the outer wall of the pipeline so that an ultrasonic wave transmission surface thereof is in parallel to a pipe axis direction of the pipeline, and another at least one of the ultrasonic wave elements is an ultrasonic wave reception element and is attached to the outer wall of the pipeline so that an ultrasonic wave reception surface thereof is in parallel to the pipe axis direction of the pipeline.