A trailer refrigeration system comprising: an electricity generator; an electricity-generator engine configured to drive the electricity generator; a refrigerant circuit having an electric compressor being driven by ac electric power from a first inverter, a condenser fan being driven by ac electric power from a second inverter, an evaporator fan being driven by ac electric power from a third inverter, an electric power conversion system lying between the electricity generator and the refrigerant circuit and having a converter configured to convert ac electric power generated by the electricity generator into dc electric power; an inverter (24, 25, 26) comprising the first inverter, the second inverter, and the third invertor each configured to convert dc electric power from the converter into ac electric power; and characterized by control means configured to individually control the speed of rotation of the electricity-generator engine, the electric compressor, the condenser fan, and the evaporator fan, wherein the control means includes: a refrigeration equipment control part configured to control, based on the storage compartment temperature of the trailer, the output of the first inverter, the second inverter, and the third inverter to thereby control the speed of rotation of the electric compressor, the condenser fan, and the evaporator fan; and an engine control part configured to control, based on either the input/output state of the first inverter, the second inverter, and the third inverter or the input/output state of the converter, the speed of rotation of the electricity-generator engine. an electricity generator; an electricity-generator engine configured to drive the electricity generator; a refrigerant circuit having an electric compressor being driven by ac electric power from a first inverter, a condenser fan being driven by ac electric power from a second inverter, an evaporator fan being driven by ac electric power from a third inverter, an electric compressor being driven by ac electric power from a first inverter, a condenser fan being driven by ac electric power from a second inverter, an evaporator fan being driven by ac electric power from a third inverter, an electric power conversion system lying between the electricity generator and the refrigerant circuit and having a converter configured to convert ac electric power generated by the electricity generator into dc electric power; an inverter (24, 25, 26) comprising the first inverter, the second inverter, and the third invertor each configured to convert dc electric power from the converter into ac electric power; and a converter configured to convert ac electric power generated by the electricity generator into dc electric power; an inverter (24, 25, 26) comprising the first inverter, the second inverter, and the third invertor each configured to convert dc electric power from the converter into ac electric power; and characterized by control means configured to individually control the speed of rotation of the electricity-generator engine, the electric compressor, the condenser fan, and the evaporator fan, wherein the control means includes: a refrigeration equipment control part configured to control, based on the storage compartment temperature of the trailer, the output of the first inverter, the second inverter, and the third inverter to thereby control the speed of rotation of the electric compressor, the condenser fan, and the evaporator fan; and an engine control part configured to control, based on either the input/output state of the first inverter, the second inverter, and the third inverter or the input/output state of the converter, the speed of rotation of the electricity-generator engine. a refrigeration equipment control part configured to control, based on the storage compartment temperature of the trailer, the output of the first inverter, the second inverter, and the third inverter to thereby control the speed of rotation of the electric compressor, the condenser fan, and the evaporator fan; and an engine control part configured to control, based on either the input/output state of the first inverter, the second inverter, and the third inverter or the input/output state of the converter, the speed of rotation of the electricity-generator engine.