To provide an auxiliary chair for sitting straight, which has no extra projection and is comfortably used and is extremely compactly reduced in size when not in use.

The both upper and lower surfaces of a chair body 11 are connected by inner hollow hanging, and a storage part 14 to be allowed for storage from an external part is formed on the inner side of the upper surface 11a in the inner hanging. The chair body 11 is put into a carrier-bag 12. Besides, the closed mouth part 12a of the carrier-bag 12 and a closing string 15 closing the mouth part are stored inside the storage part 14.