There is provided a method of depositing a Ge—Sb—Te thin film, including: a Ge—Sb—Te thin-film forming step of feeding and purging a first precursor including any one of Ge, Sb and Te, a second precursor including another one of Ge, Sb and Te and a third precursor including the other one of Ge, Sb and Te into and from a chamber in which a wafer is mounted and forming the Ge—Sb—Te thin film on the wafer; and a reaction gas feeding step of feeding reaction gas while any one of the first to third precursors is fed.