The apparatus includes a heating roller that generates heat for melting toner attached to a printing medium; a first induction coil that is disposed outside the heating roller and heats the heating roller by using induced current generated according to current flowing through the first induction coil; two second induction coils that are disposed at upper portions of both ends of the first induction coil and heat the heating roller by using induced current generated according to current flowing through the two second induction coils; a power supply unit that supplies current to the first induction coil and the two second induction coils; and a control unit that controls the power supply unit to supply current flowing in the same direction or different directions to the first induction coil and the second induction coils according to the size of paper fed into the heating roller.