The invention relates to an air-conditioner and control method thereof, aiming to prevent the phenomenon that the refrigerating agent supply is insufficient or excessive in each indoor machine even if an outdoor machine is operated by connecting multiple indoor machines with different connecting types (cabinet type or wall hanging type) and capacities. For said purpose, in an air-conditioner which includes one outdoor machine comprising a compressor, a first indoor machine which does not provide the running state information to the outdoor machine and a second indoor machine that provides the running state information to the outdoor machine, the air-conditioner control method according to the invention includes following steps: detecting an outdoor temperature; determining a compressor target output temperature corresponding to the outdoor temperature; detecting an output temperature of the compressor; controlling the opening degree of an expansion valve for providing the refrigerating agent to the first indoor machine so as to make the output temperature of the compressor follow the target output temperature.