A gas flowmeter includes: device body (1) which air-tightly accommodates a fluid to be measured; an inlet pipe through which the fluid to be measured is made to flow into device body (1); and outlet pipe (5) through which the fluid to be measured is made to flow out from device body (1). The gas flowmeter further includes: ultrasonic flow rate measuring unit (9) which is connected to outlet pipe (5) and measures a flow rate of the fluid to be measured which flows in ultrasonic flow rate measuring unit (9); connecting pipe (7) which is connected to outlet pipe (5); and flow passage member (10) which is connected to connecting pipe (7) and has a flow passage shape identical to a shape of ultrasonic flow rate measuring unit (9). The gas flowmeter is provided with support member (11) which fixes ultrasonic flow rate measuring unit (9) and flow passage member (10) to each other. With such a configuration, a gas flow meter capable of performing stable flow rate measurement can be implemented.
