To provide an induction heating device with a bar and induction heating method capable of accurately control the temperature of the bar stock at every part in the direction of width even for the bar having a deformed cross section.

The induction heating device comprises a bar transfer mechanism, a channel type inductor 12, 18 arranged so as to face with both surfaces of the bar, and a high frequency power source supplying high frequency current to the inductors. A coil serving as the channel type inductors 12, 18 is composed of a pair of detour parts 12B detouring the edge side of the bar T, first parts 12C connecting one ends of the detour parts 12B to each other, facing the first surface of the bar, and second parts 12D connecting the other ends of the detour parts 12B to each other, facing the second surface of the bar. The direction of the current flowing through first parts 12C and the second parts 12D are reversed from each other. By setting the frequency of the high frequency current from the high frequency power source lower than critical frequency at a thin part of the bar, a thick part and the thin part of the bar are heated with approximately the same temperature with ease.