An air pump is capable of inflating an inflatable object, and includes a housing unit, a motor and a fan. The motor and the fan are disposed within the housing unit. The housing unit is formed with a pair of first and second intake port units and an exhaust port unit. The fan includes a middle plate connected fixedly to a driving shaft of the motor, and a pair of first and second fan blade units extending respectively from two opposite side surfaces of the middle plate. Air is sucked into the housing unit by the first and second fan blade units through the first and second intake port units, respectively, and is subsequently forced out of the housing unit by the first and second fan blade units through the exhaust port unit.