An iron core annealing furnace that is used in annealing of an amorphous iron core requiring strict control of annealing temperature. There is provided an iron core annealing furnace comprising a furnace body fitted at its superior area with a heat source and a fan, wherein the furnace body has a double layer structure consisting of a furnace interior defined by the inside division wall of the furnace body and an interspace defined by the division wall and the outside wall of the furnace body, and wherein the fan is disposed in the center of a superior area of the furnace body, and wherein the fan is adapted to introduce hot air from the furnace interior of the double layer structure, feed the hot air to the outside of the double layer structure, allow the hot air to enter the furnace interior from an inferior area of the furnace body and heat the iron core, and circulate the hot air.