Image forming apparatus and storage method capable of suppressing occurrence of high-temperature offset

An image forming apparatus, comprising:

• a fixing portion configured to fix a toner image transferred onto a sheet to the sheet;
• a first storage processing portion configured to store in a volatile first storage portion width size information corresponding to a size in a width direction of a sheet perpendicular to a conveying direction of the sheet after the sheet has passed a fixing position of the toner image by the fixing portion;
• a determination processing portion configured to, using the width size information last stored in the first storage portion, determine, in a case in which an image forming process for forming an image on the sheet is executed, whether or not a temperature lowering process for lowering a temperature of the fixing portion is necessary;
• a second storage processing portion configured to, in a case in which power supply to the first storage portion is stopped, store the width size information last stored in the first storage portion in a non-volatile second storage portion;
• a third storage processing portion configured to, in a case in which power supply to the first storage portion is started, store, in the first storage portion, the width size information that was last stored in the second storage portion;
• and
• a fourth storage processing portion configured to, after the width size information is stored by the third storage processing portion, store, in the second storage portion, the width size information corresponding to the size in the width direction of the sheet having a minimum size in the width direction among the sheets on which an image can be formed by the image forming apparatus.