To provide an air pump in which a suction/exhaust efficiency is not reduced by unbalance of a plurality of pump chambers.

The air pump 10 is provided with the pump chamber P1, P2 constituted by suction chambers 33, 63 having suction ports 33a, 63a and exhaust chambers 32, 62 having exhaust ports 32a, 62a; a plurality of cylinder chambers 47, 48; diaphragms 13, 14 reciprocatedly provided; and a crank mechanism 20 for reciprocating the diaphragms 13, 14. When the diaphragms 13, 14 are advanced respectively, external air is suctioned to the cylinder chambers 47, 48 through the suction ports 33a, 63a and the suction chambers 33, 63 respectively. When the diaphragms 13, 14 are returned respectively, the air in the cylinder chambers 47, 48 is exhausted to the outside through the exhaust chambers 32, 62 and the respective exhaust ports 32a, 62a respectively. The respective suction chambers 33, 63 of the respective pump chambers P1, P2 are communicated with each other and the respective exhaust chambers 32, 62 are communicated with each other.