To provide a fixing unit which can prevent the occurrence of abnormal images and stains on the images.

This fixing unit uses a soft roller 4 made of an elastic material 2 covering a core metal 1 with its surface 3 covered with a film to increase peeling as a fixing roller to fix the paper carrying an toner image yet to fix by passing it through the nips between the pressure rollers 5. Denoting the outer diameter of the roller by D1 at both ends and D2 at the center, the pressure roller 6 made of a rigid material in a concave satisfying the relation D1>D2 is pressed to the surface of the soft roller, and the length Lp of the pressure roller and the width W of the paper passing the nip satisfies the relation Lp>W.