A turbo-refrigeration-unit control device that controls a turbo refrigeration unit, the turbo refrigeration unit comprising: a centrifugal compressor that compresses a refrigerant; a condenser that condenses a high-pressure gas refrigerant through heat exchange with a first non-refrigerant supplied by a first-non-refrigerant pump; an expansion valve that expands a liquid refrigerant derived from the condenser; an evaporator in which the expanded liquid refrigerant evaporates through heat exchange with a second non-refrigerant supplied by a second-non-refrigerant pump; a bypass-circuit control valve that is provided in a bypass circuit used to inject part of the high-pressure gas refrigerant compressed by the centrifugal compressor into a suction port of the centrifugal compressor and that controls the flow rate of the high-pressure gas refrigerant; compressor-suction-port pressure measurement means for measuring a suction pressure of the gas refrigerant at the centrifugal compressor; and second-non-refrigerant outlet temperature measurement means for measuring an outlet temperature of the second non-refrigerant at the evaporator, characterized in that, when the turbo refrigeration unit is started-up, the expansion valve is controlled so as to be closed; the first-non-refrigerant pump and the second-non-refrigerant pump are operated; the centrifugal compressor is started-up; and then the degree-of-opening of the bypass-circuit control valve is controlled such that the temperature difference between a suction saturation temperature at the centrifugal compressor and the outlet temperature of the second non-refrigerant becomes equal to or less than a predetermined temperature difference. a centrifugal compressor that compresses a refrigerant; a condenser that condenses a high-pressure gas refrigerant through heat exchange with a first non-refrigerant supplied by a first-non-refrigerant pump; an expansion valve that expands a liquid refrigerant derived from the condenser; an evaporator in which the expanded liquid refrigerant evaporates through heat exchange with a second non-refrigerant supplied by a second-non-refrigerant pump; a bypass-circuit control valve that is provided in a bypass circuit used to inject part of the high-pressure gas refrigerant compressed by the centrifugal compressor into a suction port of the centrifugal compressor and that controls the flow rate of the high-pressure gas refrigerant; compressor-suction-port pressure measurement means for measuring a suction pressure of the gas refrigerant at the centrifugal compressor; and second-non-refrigerant outlet temperature measurement means for measuring an outlet temperature of the second non-refrigerant at the evaporator, characterized in that, when the turbo refrigeration unit is started-up, the expansion valve is controlled so as to be closed; the first-non-refrigerant pump and the second-non-refrigerant pump are operated; the centrifugal compressor is started-up; and then the degree-of-opening of the bypass-circuit control valve is controlled such that the temperature difference between a suction saturation temperature at the centrifugal compressor and the outlet temperature of the second non-refrigerant becomes equal to or less than a predetermined temperature difference.