To provide an auxiliary chair by which feet neither get pain nor get impatient even after a user sits upright for a long time politely without loosening his legs.

The upright floor chair of one leg is provided by using one leg, into which a core rod 3 of the leg is inserted into a cylinder 2 of the leg, and a pipe. In the upright floor chair, a step slit 14 is engraved in a groove 18 for the core rod of the leg so as to freely adjust a sitting height corresponding to the physique, and the sitting height is adjusted by vertically moving a seat surface 4 with a ratchet 6. In the upright floor chair using the pipe, the sitting height is adjusted by joining a sitting height adjusting ring above and under the pipe. When carrying the chair, the chair is folded while overlapping a stable stand 1 on the downside and the seat surface 4 on the upside through shafts 15 and 16.