To provide an air pump that retards degradation of a diaphragm, suppresses vibration, noise and the like caused when gas is sucked and discharged, and is reduced in size.

The air pump 1 comprises: a pump case 2; and the diaphragm 20 partitioning the pump case 2 into a pump chamber 3 and a cam chamber 4, in which the pump case 2 has an inlet 3a and an outlet 3b opening into the pump chamber 3, the inlet 3a has a check valve 7a for allowing an air flow into the pump chamber 3, and the outlet 3b has a check valve 7b for allowing an air flow out of the pump chamber 3. A diaphragm support member 30 is attached to the diaphragm 20 and arranged in the cam chamber 4, a rotary shaft 40 is positioned concentrically with the diaphragm 20 and held rotatable in the pump case 2, and a drive motor 8 is disposed to drive the rotary shaft 40 axially rotatively. The diaphragm support member 30 has a driven projection 33 in a position eccentric to the center of the rotary shaft 40, a tip end 33a of the driven projection 33 is pressed on an end face of the rotary shaft 40, and the end face is formed as a cam face 41 inclined against the axis of the rotary shaft 40.