To provide a compact static pressure gas bearing unit which further stably supports a rotator rotating at high speed without contacting, by a simple structure.

Two shaft holders 3A and 3B fix an air shaft unit 1 for supporting a pulley 2 without contacting at both end portions 113 and 12. Gas is supplied from a radial bearing surface of the air shaft unit 1 into a radial bearing clearance between the radial bearing surface and an inner peripheral surface of the pulley 2, thereby forming a gas film in the radial bearing clearance. The gas is exhausted from the radial bearing clearance to thrust bearing clearances between thrust bearing surfaces 1132 and 121 of the air shaft unit 1 and a boss end surface of the pulley 2, which connects the radial bearing clearance. By using the exhaust, gas film is also formed in the thrust bearing clearance.