PURPOSE: To enable to control a desired mold temperature in a wide range, by enabling to supply both of a high temperature thermal medium and a low temperature thermal medium to a mold independently each other.

CONSTITUTION: A thermal medium is fed to the low temperature side and high temperature side medium reservoirs 19, 17 by the signal of the electrode rods provided to a liquid level control electrode tube 44. The temperature of the fed thermal medium is detected by the thermal medium sensor 35 installed at the low temperature side medium reservoir 19 and the signal is sent to the temperature setter 38 which is the vital part of a medium temperature controlling system and when it is higher than a set value, a coolant is fed to a cooler 20 for cooling from a unit 36 and the temperature of the thermal medium is lowered to make the desired low temperature medium. Meanwhile, the high temperature side medium reservoir 17 is controlled to a set temperature by a temperature sensor 34 and a heater 18. Two kinds of the temperature medium are fed eacy by the pressure pumps 21, 22 and the temperature of a mold (A) is controlled at a constant value.