Abstract: There is provided a temperature adjustment system which performs temperature adjustment of one or a plurality of instruments installed in a vehicle, the temperature adjustment system comprising: a heat medium temperature regulating device which is configured to regulate a temperature of a heat medium; a heat medium supplying device which is configured to supply, to the instrument, the heat medium subjected to temperature regulation in the heat medium temperature regulating device; a bypass flow rate regulating device which is configured to regulate a passage flow rate of the heat medium in a stepwise manner, which is provided to bypass the heat medium temperature regulating device; a temperature measuring device which is configured to measure a temperature of the instrument; and a controlling device which is configured to control the bypass flow rate regulating device based on the measured temperature.