To provide a diaphragm pump which achieves cost reduction and space saving.

Water supplied from a first suction opening 17e is sucked into each of pump chambers 16A-16D through a first suction passage 13e. Concurrently, air supplied from a second suction opening is sucked into each of the pump chambers 16A-16D via communication passages 13A-13D through second suction passages 11A-11D. A mixed fluid including the water and the air mixed with each other in each of the pump chambers 16A-16D is discharged from a discharge opening 17c through a discharge passage 13d.