A container refrigeration system includes 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.