To provide a gas meter which can contribute to maintenance of measuring precision.

The gas meter is equipped with a flow rate measuring means 46 which outputs a flow rate signal according to the passing gas flow rate of a gas meter disposed in a gas supplying line, and a flow rate measuring means 42a which measures the flow rate of gas on the basis of the flow rate signal sent from the measuring means 46. In the gas meter, a pressure measuring means 47 measuring the pressure of gas of the gas meter, a pressure flow rate calculating means 42b calculating the pressure flow rate corresponding to the pressure detected with the pressure measuring means 47, and a measuring precision judging means 42c are installed. The judging means 42c judges the decrease of measuring precision of the flow rate measuring means 46, on the basis of the flow rate measured with the flow rate measuring means 42a and the pressure flow rate calculated with the pressure flow rate calculating means 42b.