To provide an electromagnetic vibrating diaphragm pump with which improved work efficiency when assembling a diaphragm to a center plate, reduced production cost and stabilization of performance between products are possible.

A disk-shaped second plate 7b includes, in the central part of the surface that abuts on a diaphragm 4, a cruciform protruding part 21 in which depressions 20 are formed and a second ring-shaped rib 29 that is formed on the outer diameter side thereof. A disk-shaped first plate 7a has a first ring-shaped rib formed in the central part of the surface that contacts the diaphragm 4 and the first ring-shaped rib forms an assembly groove provided with protrusions that are pressed and fitted into the depressions 20. Around a central through-hole 26, the disk-shaped diaphragm 4 has diaphragm effusion-preventing protrusions 28 that protrude from each of the two surfaces of the diaphragm 4 and with which the ring-shaped ribs engage from the outer circumferential side.