PURPOSE: To form a nip width corresponding to a toner image to be fixed and to obtain the copied image of high image quality having a moderate gloss.

CONSTITUTION: Three upper or lower fixing rollers 201-203 are vertically disposed and fixing parts for a full color copy and a black-and-white copy are formed on the press-contact part of the upper fixing roller 201 with the middle fixing roller 202 and the press-contact part of the middle fixing roller 202 with the lower fixing roller 203. respectively. On the upper fixing roller 201, a pressure varying mechanism 209 changing over the pressure of the upper fixing roller 201 to the middle fixing roller 202 is provided. The operation of the pressure varying mechanism is controlled basing on a signal from an AE sensor 36 detecting the density of an original, in a control circuit 37.