Abstract: The present invention is to provides a foil gas bearing which has sufficient damping effects due to a frictional force and a sufficient stiffness to support the rotary shaft. The foil gas bearing has a rotary shaft retainer for retaining a rotary shaft; and a back spring for preventing the displacement of the rotary shaft, which is provided between rotary shaft and rotary shaft retainer. Plural protrusions are formed at one element, which is either the rotary shaft retainer or the back spring. Plural recesses are formed at the other elements, which is either the back spring or the rotary shaft retainer at places which correspond to the protrusions. The protrusions partially fit into the recesses.

Abstract: One object of the present invention is to provide a foil gas bearing which has sufficient damping effects due to a frictional force and a sufficient stiffness to support the rotary shaft; in order to achieve the object, the present invention provide a foil gas bearing comprising: a rotary shaft retainer for retaining a rotary shaft; and a back spring for preventing the displacement of said rotary shaft, which is provided between said rotary shaft and said rotary shaft retainer; wherein plural protrusions are formed at one element which is either said rotary shaft retainer or said back spring; plural recesses are formed at the other element which is either said back spring or said rotary shaft retainer at places which correspond to said protrusions; and said protrusions partially fit into said recesses.