A heat treating device for a steel plate, comprising a plurality of conveying rolls for horizontally conveying the steel plate and at least one induction heating device for heating the steel plate. The induction heating devices are disposed between the specified conveying rolls adjacent to each other. At least one pressing roll for pressing the steel plate from the upper face is installed on the outlet side of at least the induction heating device located on the upstream-most side of the induction heating devices. At least the pressing roll located on the upstream-most side of the pressing rolls is disposed oppositely to the conveying roll on the upper side of the conveying roll located on the outlet side of the induction heating device. Thus, when the induction heating device is used, also a specified heat treatment can be applied to the steel plate by the heat treatment device for the steel plate without obstructing the conveying of the steel plate.