A process for producing 1,3,3,3-tetrafluorpropene, comprising: a first step of reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride thereby obtaining 1-chloro-3,3,3-trifluoropropene; and a second step of reacting 1-chloro-3,3,3-trifluoropropene obtained by the first step with hydrogen fluoride in a gaseous phase and in the presence of a fluorination catalyst characterized in that the reaction at the time of reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride to produce 1-chloro-3,3,3-trifluoropropene in the first step is conducted in a liquid phase and in the absence of the fluorination catalyst, further characterized by passing 1,3,3,3-tetrafluoropropene obtained by the second step further through the following steps of: Step A: a step of removing an excessive amount of hydrogen fluoride, 1-chloro-3,3,3-trifluoropropene and 1,1,1,3,3-pentafluoropropane from a reaction mixture containing 1,3,3,3-tetrafluoropropene obtained by the second step; Step B: a step of further removing a remaining hydrogen fluoride after the step A; and Step C: a step of removing hydrogen chloride (HCl) from 1,3,3,3-tetrafluoropropene obtained by the step B, further characterized in that, in the first step hydrogen chloride and 1-chloro-3,3,3-trifluoropropene generated in the reaction are extracted from the reaction system, and further characterized in that the fluorination catalyst used when reacting 1-chloro-3,3,3-trifluoropropene with a fluorination agent in the gaseous phase and in the presence of the fluorination catalyst in the second step is: activated carbon; activated carbon that carries oxide, fluoride, chloride, fluorinated chloride, oxyfluoride, oxychloride or oxyfluorinated chloride of one kind or two or more kinds of metals selected from chromium, titanium, aluminum, manganese, nickel, cobalt and zirconium, thereon; alumina, fluorinated alumina; aluminum fluoride; zirconia; or fluorinated zirconia. a first step of reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride thereby obtaining 1-chloro-3,3,3-trifluoropropene; and a second step of reacting 1-chloro-3,3,3-trifluoropropene obtained by the first step with hydrogen fluoride in a gaseous phase and in the presence of a fluorination catalyst characterized in that the reaction at the time of reacting 1,1,1,3,3-pentachloropropane with hydrogen fluoride to produce 1-chloro-3,3,3-trifluoropropene in the first step is conducted in a liquid phase and in the absence of the fluorination catalyst, further characterized by passing 1,3,3,3-tetrafluoropropene obtained by the second step further through the following steps of: Step A: a step of removing an excessive amount of hydrogen fluoride, 1-chloro-3,3,3-trifluoropropene and 1,1,1,3,3-pentafluoropropane from a reaction mixture containing 1,3,3,3-tetrafluoropropene obtained by the second step; Step B: a step of further removing a remaining hydrogen fluoride after the step A; and Step C: a step of removing hydrogen chloride (HCl) from 1,3,3,3-tetrafluoropropene obtained by the step B, Step A: a step of removing an excessive amount of hydrogen fluoride, 1-chloro-3,3,3-trifluoropropene and 1,1,1,3,3-pentafluoropropane from a reaction mixture containing 1,3,3,3-tetrafluoropropene obtained by the second step; Step B: a step of further removing a remaining hydrogen fluoride after the step A; and Step C: a step of removing hydrogen chloride (HCl) from 1,3,3,3-tetrafluoropropene obtained by the step B, further characterized in that, in the first step hydrogen chloride and 1-chloro-3,3,3-trifluoropropene generated in the reaction are extracted from the reaction system, and further characterized in that the fluorination catalyst used when reacting 1-chloro-3,3,3-trifluoropropene with a fluorination agent in the gaseous phase and in the presence of the fluorination catalyst in the second step is: activated carbon; activated carbon that carries oxide, fluoride, chloride, fluorinated chloride, oxyfluoride, oxychloride or oxyfluorinated chloride of one kind or two or more kinds of metals selected from chromium, titanium, aluminum, manganese, nickel, cobalt and zirconium, thereon; alumina, fluorinated alumina; aluminum fluoride; zirconia; or fluorinated zirconia.