An advanced humid air gas turbine system comprising: a gas turbine system that includes a compressor for compressing air, a compressed air header for mixing high-pressure air introduced from the compressor with steam to generate humidified combustion air, a combustor for mixing combustion air from the compressed air header with fuel for sake of combustion so as to generate combustion gas, and a turbine driven by the combustion gas that is generated by the combustor; a heat recovery steam generator for generating steam by use of exhaust gas from the turbine; a water recovery system disposed on a downstream side of the heat recovery steam generator, the water recovery system recovering moisture contained in the exhaust gas, characterized in further comprising: a first steam system comprising a superheated steam adjusting valve, a pipe connecting the superheater section of the heat recovery steam generator to a superheated steam adjusting valve, and another pipe; and a second steam system comprising a steam nozzle adjusting valve, a steam nozzle, and a further pipe connecting the steam nozzle adjusting valve to the steam nozzle; wherein the first steam system is adapted to supply steam, coming from a superheater section of the heat recovery steam generator, through the pipes (52, 55) and the superheated steam adjusting valve to the compressed air header; and the second steam system is adapted to supply steam, coming from the superheater section of the heat recovery steam generator, through the steam nozzle adjusting valve, the further pipe and the steam nozzle into an exhaust gas passage of the heat recovery steam generator or to the water recovery system, wherein the advanced humid air gas turbine system is adapted to block the first steam system by closing operation of the superheated steam adjusting valve and to make the second steam system communicate with the heat recovery steam generator by opening operation of the steam nozzle adjusting valve, when the gas turbine system is starting up, shut down, or subjected to load rejection, in order to recover steam coming from the heat recovery steam generator. a gas turbine system that includes a compressor for compressing air, a compressed air header for mixing high-pressure air introduced from the compressor with steam to generate humidified combustion air, a combustor for mixing combustion air from the compressed air header with fuel for sake of combustion so as to generate combustion gas, and a turbine driven by the combustion gas that is generated by the combustor; a heat recovery steam generator for generating steam by use of exhaust gas from the turbine; a water recovery system disposed on a downstream side of the heat recovery steam generator, the water recovery system recovering moisture contained in the exhaust gas, characterized in further comprising: a first steam system comprising a superheated steam adjusting valve, a pipe connecting the superheater section of the heat recovery steam generator to a superheated steam adjusting valve, and another pipe; and a second steam system comprising a steam nozzle adjusting valve, a steam nozzle, and a further pipe connecting the steam nozzle adjusting valve to the steam nozzle; wherein the first steam system is adapted to supply steam, coming from a superheater section of the heat recovery steam generator, through the pipes (52, 55) and the superheated steam adjusting valve to the compressed air header; and the second steam system is adapted to supply steam, coming from the superheater section of the heat recovery steam generator, through the steam nozzle adjusting valve, the further pipe and the steam nozzle into an exhaust gas passage of the heat recovery steam generator or to the water recovery system, wherein the advanced humid air gas turbine system is adapted to block the first steam system by closing operation of the superheated steam adjusting valve and to make the second steam system communicate with the heat recovery steam generator by opening operation of the steam nozzle adjusting valve, when the gas turbine system is starting up, shut down, or subjected to load rejection, in order to recover steam coming from the heat recovery steam generator. a first steam system comprising a superheated steam adjusting valve, a pipe connecting the superheater section of the heat recovery steam generator to a superheated steam adjusting valve, and another pipe; and a second steam system comprising a steam nozzle adjusting valve, a steam nozzle, and a further pipe connecting the steam nozzle adjusting valve to the steam nozzle; wherein the first steam system is adapted to supply steam, coming from a superheater section of the heat recovery steam generator, through the pipes (52, 55) and the superheated steam adjusting valve to the compressed air header; and the second steam system is adapted to supply steam, coming from the superheater section of the heat recovery steam generator, through the steam nozzle adjusting valve, the further pipe and the steam nozzle into an exhaust gas passage of the heat recovery steam generator or to the water recovery system, wherein the advanced humid air gas turbine system is adapted to block the first steam system by closing operation of the superheated steam adjusting valve and to make the second steam system communicate with the heat recovery steam generator by opening operation of the steam nozzle adjusting valve, when the gas turbine system is starting up, shut down, or subjected to load rejection, in order to recover steam coming from the heat recovery steam generator.