Disclosed is an air conditioner for creating a comfortable indoor environment. The air conditioner includes an indoor unit configured to have a carbon dioxide remover for filtering carbon dioxide from indoor air to supply clean air into a room, and discharging the filtered carbon dioxide to the outside, an outdoor unit configured to have an oxygen generator for separating oxygen from outdoor air introduced from the outside to supply the separated oxygen into the room, and discharging residues from which the oxygen is separated to the outside; and a processor configured to control the carbon dioxide remover and the oxygen generator to discharge the filtered carbon dioxide and the residues to the outdoor together. According to the disclosure, by first removing the carbon dioxide from the room and then discharging the carbon dioxide and the residues while operating the oxygen generator, a piping installation operation by a simple piping structure as well as an efficient operation is possible.