A fluid temperature control system according to an embodiment cools a fluid by means of a multiple refrigeration apparatus including a high-temperature-side refrigerator, a medium-temperature-side refrigerator and a low-temperature-side refrigerator. The medium-temperature-side refrigerator in the multiple refrigeration apparatus has a medium-temperature-side first evaporator and a medium-temperature-side second evaporator. A high-temperature-side evaporator of the high-temperature-side refrigerator and a medium-temperature-side condenser of the medium-temperature-side refrigerator constitute a first cascade condenser. The medium-temperature-side second evaporator of the medium-temperature-side refrigerator and a low-temperature-side condenser of the low-temperature-side refrigerator constitute a second cascade condenser. The fluid allowed to flow by a fluid flow apparatus is cooled by the medium-temperature-side first evaporator of the medium-temperature-side refrigerator, and is then cooled by the low-temperature-side evaporator of the low-temperature-side refrigerator.