Abstract: A liquid temperature regulator is disclosed which includes a refrigeration cycle comprising a compressor, a condenser and an evaporator, a liquid tank containing a kind of liquid to be temperature-controlled and the evaporator, and inlet and outlet tubes for feeding the liquid into the tank and feeding out the liquid from the tank. The regulator is provided with a by-pass path for the connection of the outlet and inlet ports of the compressor, a valve for opening and closing the valve and a temperature controller for controlling the valve according to the temperature of the liquid. The by-pass path is closed when the liquid temperature is higher than a preset value and it is closed when the liquid temperature is lower than the value.