One or more materials selected from 1,1,1,3,3-pentachloropropane, 1,1,3,3-tetrachloropropene and 1,3,3,3-tetrachloropropene are used as the specific materials described above. Before submitting the materials and HF to a fluorination reaction, almost all water is removed from them.To continuously manufacture useful intended products efficiently as well as to prevent deactivation of the catalyst and the accumulation of organic substances with high boiling points when manufacturing said useful 1,1,1,3,3-pentafluoropropane and/or 1-chloro-3,3,3-trifluoropropene, by fluorinating the specific materials with HF in the presence of a catalyst.