To provide a diaphragm flow meter evaluating method capable of representing behaviors shown by articles actually recovered from markets.

For evaluating the performance of a diaphragm flow meter in which a flow detecting part is provided with a diaphragm part provided in a state in which its peripheral part is fixed to a casing, which forms a measuring chamber, and reciprocated by the supply and discharge of gas for and from the measuring chamber, the diaphragm flow meter is left in a thermal environment higher than ordinary temperatures for evaluation time between 200-4000 hours, and the diaphragm flow meter is evaluated on the basis of its performance after leaving it.