A gas meter includes a meter body having a meter inlet into which a fluid-to-be-measured is to flow and a meter outlet from which the fluid-to-be-measured is to flow out, and an extended section extending from the meter inlet to an interior of the meter body. The gas meter further includes a flow rate measurement unit inside the meter body, the flow rate measurement unit having a measurement flow passage having a straight tubular shape, a lead-in port and a lead-out port for the fluid-to-be-measured, and a shutoff valve in an internal passage of the extended section. The lead-in port is airtightly connected to the extended section so as to communicate with the internal passage.