To provide an inexpensive dynamic pressure air bearing having sufficient rigidity enough to endure high speed rotation without forming a dynamic pressure groove such as a herringbone in a fixed shaft or a rotor.

The dynamic pressure air bearing comprises the fixed shaft 1, the cylindrical rotor 2 fitted to the outer periphery side of the fixed shaft 1 at a space for rotation relative to the fixed shaft 1, and a flange 3 provided on the outer periphery side of the rotor 2. The flange 3 has a plurality of protruded portions 32 on the inner peripheral face opposed to the outer peripheral face of the rotor 2, whereby the rotor 2 is locally deformed to form a plurality of protrusions on the inner peripheral face 22 of the rotor 2 which generate dynamic pressure during rotation.