A four-compression-chamber diaphragm pump with multiple effects includes an eccentric roundel mount with four cylindrical eccentric roundels, a pump head body with four operating holes, and a diaphragm membrane with four annular positioning protrusions. A basic curved groove or other vibration-reducing first positioning structure is circumferentially disposed around each operating hole while a basic curved protrusion or other second vibration-reducing second positioning structure is provided in the diaphragm membrane for suitably coupling with the corresponding groove or other first positioning structure upon assembly, resulting in a shortened length of moment arm from the basic curved protrusions or other vibration-reducing positioning structures to respective downwardly-extending annular positioning protrusions in the diaphragm membrane, and consequently reduced vibration noise and resonant shaking in comparison with a conventional four-compression-chamber diaphragm pump. The cylindrical eccentric roundels each comprises an annular positioning groove arranged to receive one of the downwardly-extending annular positioning protrusions of the diaphragm membrane and a sloped top ring extending between annular positioning groove and a vertical or inverted frustoconical flank of the eccentric roundel, resulting in an extended service lifespan of the four-compression-chamber diaphragm pump.