To provide a constant capacity type diaphragm pump having a structure capable of delivering constant capacity and limiting dead space in a pump chamber as much as possible for preventing air lock.

The constant capacity type diaphragm pump consists of a coil 3 on which pulse current is applied, a plunger 15 reciprocated by intermittent magnetic force generated by the coil 3, a diaphragm 25 moved by the plunger 15 and a pair of check valves 36, 38 moving together by reciprocating motion of the diaphragm 25, and moreover consists of a stroke regulating part 19 provided in an anti-diaphragm side of the plunger 15, and a convex shape 29 provided in an anti-plunger side of the diaphragm 25 and adhering on a pump main body 28 when pulse current is turned off.