Air conditioner

An air conditioner, comprising:

• a controller;
• at least one compressor that compresses a refrigerant;
• at least one outdoor heat exchanger through which the refrigerant discharged from the at least one compressor flows;
• a plurality of expansion valves that expands the refrigerant passed through the at least one outdoor heat exchanger;
• a plurality of indoor heat exchangers through which the refrigerant passed through the plurality of expansion valves flows;
• a plurality of connection pipes that connects the plurality of indoor heat exchangers and the at least one compressor;
• and
• a plurality of variable valves installed in the plurality of connection pipes, wherein an opening degree of each of the plurality of variable valves is adjustable via the controller, and wherein the opening degree of the variable valve is adjusted by the controller based on an error, which is a difference between a current temperature of refrigerant at an inlet side of the respective indoor heat exchanger and a target temperature, and an error slope, which is a temperature change of the refrigerant at the inlet side of the respective indoor heat exchanger for a predetermined period of time.