A gas treatment equipment (1, 1A-1E) for a nuclear power plant, the nuclear power plant comprising a primary containment vessel, the gas treatment equipment (1, 1A-1E) comprising: a gas treatment apparatus (2, 14, 16, 18, 20) for treating gas components included in gas supplied from the primary containment vessel of the nuclear power plant; and a mist separator, wherein said gas treatment apparatus (2, 14, 16, 18, 20) includes a casing (3, 3A) and a gas component treatment member (22, 15, 17, 19, 21) installed in said casing (3, 3A) for treating said gas components; wherein a heat exchanger (4, 4A) is installed in said casing (3, 3A), the heat exchanger (4, 4A) being arranged to heat gas in the casing (3, 3A) being supplied to the gas component treatment member (22, 15, 17, 19, 21), wherein the heat exchanger (4, 4A) is arranged to heat the gas in the casing (3, 3A) by heat exchange from a gas, which includes steam and said gas components, supplied to the heat exchanger (4, 4A) from a primary containment vessel of a nuclear power plant, to the gas in said casing (3, 3A); wherein said mist separator is connected to said heat exchanger (4, 4A) and is arranged to remove mists that are generated in said heat exchanger (4, 4A) by condensation of said steam in said gas supplied from the primary containment vessel of the nuclear power plant, together with a part of said gas components adsorbed to said mists; and wherein a pipe path is provided between said mist separator and said casing (3, 3A) for introducing said gas supplied from the primary containment vessel of the nuclear power plant including said gas components not removed by said mist separator, which is output from said mist separator, into said casing (3, 3A) to be supplied to the gas component treatment member (22, 15, 17, 19, 21). a gas treatment apparatus (2, 14, 16, 18, 20) for treating gas components included in gas supplied from the primary containment vessel of the nuclear power plant; and a mist separator, wherein said gas treatment apparatus (2, 14, 16, 18, 20) includes a casing (3, 3A) and a gas component treatment member (22, 15, 17, 19, 21) installed in said casing (3, 3A) for treating said gas components; wherein a heat exchanger (4, 4A) is installed in said casing (3, 3A), the heat exchanger (4, 4A) being arranged to heat gas in the casing (3, 3A) being supplied to the gas component treatment member (22, 15, 17, 19, 21), wherein the heat exchanger (4, 4A) is arranged to heat the gas in the casing (3, 3A) by heat exchange from a gas, which includes steam and said gas components, supplied to the heat exchanger (4, 4A) from a primary containment vessel of a nuclear power plant, to the gas in said casing (3, 3A); wherein said mist separator is connected to said heat exchanger (4, 4A) and is arranged to remove mists that are generated in said heat exchanger (4, 4A) by condensation of said steam in said gas supplied from the primary containment vessel of the nuclear power plant, together with a part of said gas components adsorbed to said mists; and wherein a pipe path is provided between said mist separator and said casing (3, 3A) for introducing said gas supplied from the primary containment vessel of the nuclear power plant including said gas components not removed by said mist separator, which is output from said mist separator, into said casing (3, 3A) to be supplied to the gas component treatment member (22, 15, 17, 19, 21).