To provide a device and method of heating/cooling a metallic body capable of quickly cooling and/or heating the metallic body by using a heat medium with a simple structure.

A rotary cylinder 3 of a diameter slightly smaller than that of a circular hole 2a, is inserted to the circular hole 2a penetrating through the metallic body 2, an opening section 3f is formed on a side section of a circumference of the rotary cylinder 3, an outer edge section 3g at a back side in the rotating direction of the opening section 3f takes the form of acute angle, an inlet 6 and an outlet 7 for the heat medium are respectively formed on an upper part and a lower part of the rotary cylinder 3, and further the rotary cylinder 3 can be rotated while adjusting its rotating speed.