Air conditioner capable of a cooling/heating mixed operation in which a refrigerant circulates through a refrigerant circuit formed by connecting, with piping: a heat-source side unit having a heat-source side heat exchanger and a compressor; a plurality of load-side units each having a load-side throttle device and a load-side heat exchanger; and a cooling / heating branch unit having a gas / liquid separator for supplying a gas refrigerant to said load-side unit that carries out a heating operation and for supplying a liquid refrigerant to said load-side unit that carries out a cooling operation, the air conditioner comprising: a bypass pipe forming a bypass into which the refrigerant discharged by said compressor is split to flow into piping leading to the inlet side of the refrigerant when the heat-source side heat exchanger functions as an evaporator; an opening / closing valve for bypass that controls a split flow of the refrigerant to said bypass pipe by opening / closing; a throttle device for bypass for controlling an amount of said split refrigerant provided to said bypass; and control means for executing processing in which it is judged if there is an abnormal rise or a fear of the abnormal rise in a refrigerant pressure on the discharge side of said compressor when an operation is performed that said heat-source side heat exchanger functions as an evaporator and at least one of said load-side heat exchangers functions as a condenser and if it is judged that there is the abnormal rise or a fear thereof, said opening / closing valve for bypass is made to open and an opening degree of said throttle device for bypass is controlled on the basis of a pressure of the refrigerant on the discharge side of said compressor so as to split the refrigerant to said bypass pipe. a heat-source side unit having a heat-source side heat exchanger and a compressor; a plurality of load-side units each having a load-side throttle device and a load-side heat exchanger; and a cooling / heating branch unit having a gas / liquid separator for supplying a gas refrigerant to said load-side unit that carries out a heating operation and for supplying a liquid refrigerant to said load-side unit that carries out a cooling operation, the air conditioner comprising: a bypass pipe forming a bypass into which the refrigerant discharged by said compressor is split to flow into piping leading to the inlet side of the refrigerant when the heat-source side heat exchanger functions as an evaporator; an opening / closing valve for bypass that controls a split flow of the refrigerant to said bypass pipe by opening / closing; a throttle device for bypass for controlling an amount of said split refrigerant provided to said bypass; and control means for executing processing in which it is judged if there is an abnormal rise or a fear of the abnormal rise in a refrigerant pressure on the discharge side of said compressor when an operation is performed that said heat-source side heat exchanger functions as an evaporator and at least one of said load-side heat exchangers functions as a condenser and if it is judged that there is the abnormal rise or a fear thereof, said opening / closing valve for bypass is made to open and an opening degree of said throttle device for bypass is controlled on the basis of a pressure of the refrigerant on the discharge side of said compressor so as to split the refrigerant to said bypass pipe. a bypass pipe forming a bypass into which the refrigerant discharged by said compressor is split to flow into piping leading to the inlet side of the refrigerant when the heat-source side heat exchanger functions as an evaporator; an opening / closing valve for bypass that controls a split flow of the refrigerant to said bypass pipe by opening / closing; a throttle device for bypass for controlling an amount of said split refrigerant provided to said bypass; and control means for executing processing in which it is judged if there is an abnormal rise or a fear of the abnormal rise in a refrigerant pressure on the discharge side of said compressor when an operation is performed that said heat-source side heat exchanger functions as an evaporator and at least one of said load-side heat exchangers functions as a condenser and if it is judged that there is the abnormal rise or a fear thereof, said opening / closing valve for bypass is made to open and an opening degree of said throttle device for bypass is controlled on the basis of a pressure of the refrigerant on the discharge side of said compressor so as to split the refrigerant to said bypass pipe.