An air pump comprising: a pump section for compressing and blowing air; and a motor section for driving the pump section, wherein a shaft of the pump section and a shaft of the motor section are integrally formed and the integral shaft is supported by at least two ball bearings, wherein a cylindrical rotor is disposed in a cylinder having a tube-shaped inner wall such that the rotor is eccentric with respect to the cylinder, a plurality of slits are axially formed in the rotor, plane-shaped vanes formed of a self-lubricating material are slidably fitted in the slits, a front plate and a rear plate are disposed at ends of the cylinder such that the rotor and vanes are disposed between the plates to define a plurality of pump spaces, a motor shaft is provided at the center axis of the rotor to configure the pump section, and a driving motor is provided at a side of the rear plate that is opposite to the pump section, whereby the driving motor drives the motor shaft to expand or contract the pump space and wherein gaps (143, 153) are respectively formed between the rotor and the front plate and the rotor and the rear plate, one of the ball bearings is set as a fixed ball bearing by fixing both inner and outer race fitting portions, the other ball bearing is set as a slidable bearing by allowing one of the inner and outer race fitting portions to be slidable, and a pre-pressure spring is disposed to elastically support the slidable bearing; characterised in that the motor section includes a motor rotor and a stator, the motor rotor is disposed such that the axial centre R of a magnet mounted on the motor rotor is biased from the axial centre S of the stator to the pump section, and the pre-pressure spring is disposed to push the rotor to the motor section. a pump section for compressing and blowing air; and a motor section for driving the pump section, wherein a shaft of the pump section and a shaft of the motor section are integrally formed and the integral shaft is supported by at least two ball bearings, wherein a cylindrical rotor is disposed in a cylinder having a tube-shaped inner wall such that the rotor is eccentric with respect to the cylinder, a plurality of slits are axially formed in the rotor, plane-shaped vanes formed of a self-lubricating material are slidably fitted in the slits, a front plate and a rear plate are disposed at ends of the cylinder such that the rotor and vanes are disposed between the plates to define a plurality of pump spaces, a motor shaft is provided at the center axis of the rotor to configure the pump section, and a driving motor is provided at a side of the rear plate that is opposite to the pump section, whereby the driving motor drives the motor shaft to expand or contract the pump space and wherein gaps (143, 153) are respectively formed between the rotor and the front plate and the rotor and the rear plate, one of the ball bearings is set as a fixed ball bearing by fixing both inner and outer race fitting portions, the other ball bearing is set as a slidable bearing by allowing one of the inner and outer race fitting portions to be slidable, and a pre-pressure spring is disposed to elastically support the slidable bearing; characterised in that the motor section includes a motor rotor and a stator, the motor rotor is disposed such that the axial centre R of a magnet mounted on the motor rotor is biased from the axial centre S of the stator to the pump section, and the pre-pressure spring is disposed to push the rotor to the motor section.