Fixing device for image forming apparatus and control method thereof

A fixing device for an image forming apparatus comprising:

• image-side rotating means for heating a side of a fixing target medium on which a toner image is formed;
• non-image-side rotating means for nipping and carrying the fixing target medium into a predetermined direction together with the image-side rotating means, and contacting a side of the fixing target medium on which the toner image is not formed;
• first heating source means for heating the image-side rotating means;
• second heating source means for heating the non-image-side rotating means with plural kinds of heating ranges including a total-length range covering a total length in the direction of a rotation axis of the non-image-side rotating means and a second range narrower than the total-length range;
• and
• control means for variably controlling power to be supplied to the first heating source means and/or the second heating source means while the image-side rotating means is carrying out an arbitrary operation mode.