An air conditioner indoor unit (100-1, ... 100-N) comprising: a communicator to receive setting information for performing air conditioning in a room from a control terminal apparatus ; and a controller that, when the indoor unit is operated as one among a plurality of indoor units included in an air conditioner that also includes one outdoor unit connected to the plurality of indoor units and configured to be operated as a cooling cycle or a heating cycle, is arranged to determine whether the received setting information is valid setting information applicable to the indoor unit depending on whether the air conditioner is being operated as the cooling cycle or the heating cycle to thereby obtain a determination result, and is arranged to set the setting information in the indoor unit depending on the determination result; wherein the controller is arranged to determine the received setting information as invalid setting information, if the outdoor unit receives setting information including an operation mode in which the outdoor unit is to be operated as the heating cycle, when the outdoor unit is being operated as the cooling cycle, and the controller is arranged to determine the received setting information as the invalid setting information, if the outdoor unit receives setting information including an operation mode in which the outdoor unit is to be operated as the cooling cycle, when the outdoor unit is being operated as the heating cycle, characterized in that the controller is arranged to determine the setting information as the valid setting information when the outdoor unit receives setting information including a heating operation mode of the indoor unit, even though the outdoor unit is being operated as the cooling cycle, if the indoor unit includes a hot water circulating pump or heat rays. a communicator to receive setting information for performing air conditioning in a room from a control terminal apparatus ; and a controller that, when the indoor unit is operated as one among a plurality of indoor units included in an air conditioner that also includes one outdoor unit connected to the plurality of indoor units and configured to be operated as a cooling cycle or a heating cycle, is arranged to determine whether the received setting information is valid setting information applicable to the indoor unit depending on whether the air conditioner is being operated as the cooling cycle or the heating cycle to thereby obtain a determination result, and is arranged to set the setting information in the indoor unit depending on the determination result; wherein the controller is arranged to determine the received setting information as invalid setting information, if the outdoor unit receives setting information including an operation mode in which the outdoor unit is to be operated as the heating cycle, when the outdoor unit is being operated as the cooling cycle, and the controller is arranged to determine the received setting information as the invalid setting information, if the outdoor unit receives setting information including an operation mode in which the outdoor unit is to be operated as the cooling cycle, when the outdoor unit is being operated as the heating cycle, characterized in that the controller is arranged to determine the setting information as the valid setting information when the outdoor unit receives setting information including a heating operation mode of the indoor unit, even though the outdoor unit is being operated as the cooling cycle, if the indoor unit includes a hot water circulating pump or heat rays. <EOS>