A container refrigeration system, comprising: a refrigerant circuit configured to perform a refrigeration cycle and including a main circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected together in this order, and a hot gas bypass circuit in which compressed refrigerant of the compressor is supplied to the evaporator by bypassing the condenser and the expansion valve; and a compressor control section configured to, in a defrosting operation in which the compressed refrigerant of the compressor returns to the compressor through the hot gas bypass circuit and the evaporator, and the evaporator is defrosted, control an operating speed of the compressor such that a pressure of the compressed refrigerant of the compressor reaches a target value, characterized in that the container refrigeration system further comprises a refrigerant amount control section configured to, depending on a superheating degree SH of the compressed refrigerant of the compressor in the defrosting operation, perform a refrigerant discharge operation in which part of the compressed refrigerant of the compressor flows into a high-pressure liquid pipe of the refrigerant circuit in which the condenser is provided, and is stored in the high-pressure liquid pipe, and a refrigerant supply operation in which the refrigerant of the high-pressure liquid pipe is supplied to the compressor. a refrigerant circuit configured to perform a refrigeration cycle and including a main circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected together in this order, and a hot gas bypass circuit in which compressed refrigerant of the compressor is supplied to the evaporator by bypassing the condenser and the expansion valve; and a main circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected together in this order, and a hot gas bypass circuit in which compressed refrigerant of the compressor is supplied to the evaporator by bypassing the condenser and the expansion valve; and a compressor control section configured to, in a defrosting operation in which the compressed refrigerant of the compressor returns to the compressor through the hot gas bypass circuit and the evaporator, and the evaporator is defrosted, control an operating speed of the compressor such that a pressure of the compressed refrigerant of the compressor reaches a target value, characterized in that the container refrigeration system further comprises a refrigerant amount control section configured to, depending on a superheating degree SH of the compressed refrigerant of the compressor in the defrosting operation, perform a refrigerant discharge operation in which part of the compressed refrigerant of the compressor flows into a high-pressure liquid pipe of the refrigerant circuit in which the condenser is provided, and is stored in the high-pressure liquid pipe, and a refrigerant supply operation in which the refrigerant of the high-pressure liquid pipe is supplied to the compressor. a refrigerant discharge operation in which part of the compressed refrigerant of the compressor flows into a high-pressure liquid pipe of the refrigerant circuit in which the condenser is provided, and is stored in the high-pressure liquid pipe, and a refrigerant supply operation in which the refrigerant of the high-pressure liquid pipe is supplied to the compressor.