An air conditioner, according to one embodiment of the present invention, comprises: a communication unit for receiving, from a terminal staying in a zone, first information of the terminal, including information on a previous staying time of the terminal in the zone; and a control unit for determining second information of the terminal, which contains an expected leaving time of the terminal, on the basis of the first information of the terminal and determining an operating mode and an operating time of the air conditioner on the basis of the second information of the terminal, and thus energy can be saved while minimizing a decline in the sensation of comfort felt by an occupant.