To highly accurately and stably control the temperature, by minimizing influence of outside air on the control temperature, by dispensing with opening-closing of an opening-closing door, even when performing various maintenances to a liquid temperature adjusting device.

When constituting this liquid temperature adjusting device 1 having a storage tank 4 having a casing 2 having the opening-closing door 3 and storing at last liquid L inside the casing 2, and a liquid circulating circuit 5 circulating the liquid L stored in the storage tank 4 to an external temperature adjusting object M by adjusting the temperature, the opening-closing door 3 is provided with one or two or more of maintenance opening parts 6a and 6b for performing inside maintenance of the casing 2 from an external part of the opening-closing door 3, and transparent opening-closing cover parts 7a and 7b are attached to these maintenance opening parts 6a and 6b.