The present invention provides an environment friendly aviation fuel base oil having combustibility, oxidation stability and excellent life cycle characteristics and contributing to diversification of primary energy, which is produced by hydrotreating a feedstock comprising a mixed oil of an oxygen-containing hydrocarbon compound originating from an animal or vegetable fat and a sulfur-containing hydrocarbon compound or a feedstock comprising said mixed oil and a petroleum base oil produced by refining crude oil and an aviation fuel composition comprising the aviation fuel base oil, and an aviation fuel composition containing such an aviation fuel base oil.