A fixing device, an image forming apparatus having the same include a fixing member having an outer peripheral face with which a sheet to be transported is brought into pressure contact, an exciting coil for induction heating of a heat generating layer of the fixing member, and an RF power supply circuit for applying a voltage of a certain drive frequency to the exciting coil. A degaussing coil is placed in small size sheet non-passing regions corresponding to end sections of the outer peripheral face of the fixing member with respect to the width direction of the sheet. A changeover switch opens or closes the degaussing coil in accordance with the size of the sheet to be transported. A control section is provided for changing and setting a drive frequency of the RF power supply circuit along with opening or closing of the degaussing coil.