Provided is a process for preparing 2-chloro-3,3,3-trifluoropropene, wherein at least one chlorine-containing compound selected from the group consisting of chloropropane represented by formula (1): CX3CHClCH2Cl, wherein each X is the same or different and each represents Cl or F, chloropropene represented by formula (2): CClY2CCl═CH2, wherein each Y is the same or different and each represents Cl or F, and chloropropene represented by formula (3): CZ2═CClCH2Cl, wherein each Z is the same or different and each represents Cl or F, is used as a starting compound, and said at least one chlorine-containing compound is reacted with hydrogen fluoride while being heated in a gaseous state in the presence of 50 ppm or more of water relative to the chlorine-containing compound. The process of the present invention makes it possible to produce 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) in a manner that is easily conducted, economically advantageous, and suitable for industrial scale production.