An outdoor unit has a compressor and an outdoor heat exchanger. Each of a plurality of indoor units has an indoor heat exchanger. The outdoor unit is connected in parallel with the plurality of indoor units to form a multi-type air conditioner system having a plurality of refrigeration cycles. A plurality of gaseous flow adjustment valves are provided to the gaseous sides of the indoor units, respectively. A plurality of liquid expansion valves are provided to the liquid sides of the indoor unit, respectively. A refrigerant super-heat degree detector detects a refrigerant super-heat degree of the outdoor heat exchanger or the indoor heat exchangers. A controller controls a capacity of the compressor and opening degrees of the gaseous flow adjustment valves in accordance with required capacities of the indoor units, and controls the liquid expansion valves in accordance with a detection output from the refrigerant super-heat degree detector such that the refrigerant super-heat degree becomes a predetermined value. The controller includes an optimum control unit for controlling opening degrees of at least one of the gaseous flow adjustment valves and the liquid expansion valves in accordance with operating states of the multi-type air conditioner system such that the operating states become optimum, respectively.