To miniaturize a construction concerned with the measurement and accurately measure a flow rate and temperature, by simplifying signal processing for flow rate and temperature measurement.

The construction includes a first propagating pathway, where ultrasonic waves that transmit and receive between a first ultrasonic vibrator 6 and a second ultrasonic vibrator 7, are reflected at least one time by the surface 10a of the inner wall in a flow passage 10, and a second propagating pathway, where ultrasonic waves that transmit and receive between a first ultrasonic vibrator 6 and a second ultrasonic vibrator 8, are propagated from the flow passage 10 to the outside of a measuring pipe 5 at a reflecting part on the way of the first propagating pathway. Then, the flow rate of a fluid 9, passing through the flow passage 10 by the difference between the propagating times of the bothways on the first propagating pathway, is measured. Also, the temperature of the fluid 9, passing through the flow passage 10 by the difference between the propagating times on the first propagating and the second propagating pathways, is measured.