Abstract: In a billet induction heating device, a plurality of heating coil units having round holes different in diameter from one another are arranged in such a manner that the central axial lines of the round holes are in parallel with one another and are in a vertical plane, and moving means supports the heating coil units thus arranged. Whenever a billet is given which is different in size from the one which has been processed, among from the heating coil units one suitable for the given billet is selected, and the moving means is operated to move the heating coil units until the selected heating coil unit reaches the position where it can accommodate the given billet. This arrangement makes it possible to achieve the replacement of the heating coil unit quickly and readily.