Fixing device, image forming apparatus and surface restoration method

A fixing device comprising:

• a fixing side member disposed on a fixing side of a sheet on which a toner image is formed;
• a back side supporting member configured to form a fixing nip for conveying the sheet in a tightly sandwiching manner in a state where the back side supporting member is brought in pressure contact with the fixing side member;
• a fixing nip width changing section configured to change a fixing nip width of the fixing nip;
• and
• a control section configured to control the fixing nip width changing section such that the fixing nip width is smaller than a fixing nip width for use in a fixation, and to rotate the fixing side member and the back side supporting member at different circumferential speeds so as to restore a surface of the fixing side member, wherein
• the control section controls the fixing nip width such that a circumferential speed difference between the fixing side member and the back side supporting member is equal to a predetermined circumferential speed difference.