To make a mold temperature in molding constant by a method wherein a heating means adjusting a temperature of a heating medium is arranged in a conveyance route of the heating medium from a reserving means to the mold.

A mold temperature controller has a heating medium such as water or oil or the like for heating a mold 4, and a reserving means 5 reserving the heating medium. Then, a heating means 2 and control means 3 controlling that are arranged in a conveyance route of the heating medium from an output opening 11 of a conveyance means 1 such as a pump or the like to the mold 4. By controlling the heating means 2 such as a sensible heater or the like by a control means 3 based on a detection temperature with a heating medium temperature detecting temperature sensor 3 in a conveyance route of a small heat capacity of the heating medium thus, a temperature of the heating medium becomes capable of being controlled accurately. Further, control means 52 controls by heating a temperature of the heating medium in the reserving means 5 near to a control temperature based on the detected temperature of the heating medium in the reserving means 5 with a reserving means temperature detecting sensor 521.