A fixing unit for fixing a toner image onto paper has a member to be heated and a pressurizing member configured to press against the member to be heated and fix the toner image to the paper. At least one coil surface is disposed along one surface of the member to be heated and includes a coil to generate a magnetic field for inductively heating the member. A magnetism shielding member is disposed near the coil surface. A switch includes a first member to allow passage of the magnetic field and a second member to prevent passage of the magnetic field. The amount of heat for the member when the switch is in a first position where the second member is close to the magnetism shielding member is smaller than when the switch is in a second position where the second member is distanced from the magnetism shielding member.