To provide a static pressure gas bearing which comprises assembly parts and has a self-aligning function.

The static pressure gas bearing 1 is composed of an inner cylindrical case 2 which is oppositely arranged to the outer circumference of an axis and an outer cylindrical case 3 which is oppositely arranged in the inner circumference of housing H, and a radial bearing face 3a and a thrust bearing face 3b are established in the surface where an inner cylindrical case or an outer cylindrical case counters mutually and a bearing face is established in the inside of the static pressure gaseous bearing. An O-ring 4 is provided on the face of the back side to the radial bearing gap and a spring 5 is provided to the case which is the face of the back side to the thrust bearing gap and is equipped with the O-ring. While absorbing an uneven gap amount of an axis and housing by the O-ring and the spring, the outer cylindrial case is moved so that an outer cylindrical may follow an angle change of an axis and housing to allow a head to be shaken continuously.