In a diaphragm type gas meter, one crank plate pivotally mounting a pair of diaphragm movement transmission levers and the other crank plate pivotally mounting a pair of valve actuating levers overlap each other rockably around the central axis of a crank shaft. The relative angular position of the two plates is controlled e.g. by an eccentric cam. On a diaphragm control wall member for restricting the stroke end of the reciprocation of each measuring diaphragm of said gas meter are formed two inclined diaphragm control surfaces with different angles of inclination. Further, on a lower casing of the gas meter is integrally die-cast a partition wall with triangular section flush with the top surface of the lower casing and defining a discharge-side valve chamber and a discharge passage.