A fixing device for fixing a toner image on a recordation medium, comprising: at least two rotation members (16, 17), at least one of said rotation members (16, 17) including a heat generation layer extending in parallel to an axis of one of the rotation members (16, 17); and a heat applying device arranged in the vicinity of one of the rotation members (16, 17), said heat applying device including: an exciting coil configured to create a magnetic flux for generating induction heat in the heat generation layer; and at least two demagnetizing coils each forming a loop space, the demagnetizing coils being stacked in at least two layers partially overlying the exciting coil and configured to cancel the magnetic flux at least at one axial end of the pair of rotation members (16, 17), said at least two demagnetizing coils being partially overlapping each other in a direction perpendicular to said loop spaces; characterized in that: the heat applying device further includes: central core members at a middle portion of the heat applying device, said central core members being made of magnetic material, central core members are provided aligning on a same line in parallel to said axis within said loop spaces of the demagnetizing coils, wherein respective central core members have different heights when in comparison to each other in said direction perpendicular to said loop spaces. at least two rotation members (16, 17), at least one of said rotation members (16, 17) including a heat generation layer extending in parallel to an axis of one of the rotation members (16, 17); and a heat applying device arranged in the vicinity of one of the rotation members (16, 17), said heat applying device including: an exciting coil configured to create a magnetic flux for generating induction heat in the heat generation layer; and at least two demagnetizing coils each forming a loop space, the demagnetizing coils being stacked in at least two layers partially overlying the exciting coil and configured to cancel the magnetic flux at least at one axial end of the pair of rotation members (16, 17), said at least two demagnetizing coils being partially overlapping each other in a direction perpendicular to said loop spaces; characterized in that: the heat applying device further includes: central core members at a middle portion of the heat applying device, said central core members being made of magnetic material, central core members are provided aligning on a same line in parallel to said axis within said loop spaces of the demagnetizing coils, wherein respective central core members have different heights when in comparison to each other in said direction perpendicular to said loop spaces. an exciting coil configured to create a magnetic flux for generating induction heat in the heat generation layer; and at least two demagnetizing coils each forming a loop space, the demagnetizing coils being stacked in at least two layers partially overlying the exciting coil and configured to cancel the magnetic flux at least at one axial end of the pair of rotation members (16, 17), said at least two demagnetizing coils being partially overlapping each other in a direction perpendicular to said loop spaces; the heat applying device further includes: central core members at a middle portion of the heat applying device, said central core members being made of magnetic material, central core members are provided aligning on a same line in parallel to said axis within said loop spaces of the demagnetizing coils, wherein respective central core members have different heights when in comparison to each other in said direction perpendicular to said loop spaces. central core members at a middle portion of the heat applying device, said central core members being made of magnetic material, central core members are provided aligning on a same line in parallel to said axis within said loop spaces of the demagnetizing coils, wherein respective central core members have different heights when in comparison to each other in said direction perpendicular to said loop spaces.