An image forming apparatus includes: an image forming station; heating and pressing rollers forming a fixing nip therebetween; a mechanism for changing the relative positional relation between the heating and pressing rollers between a contacting position in which they contact each other, a first spacing position in which they are spaced, and the second spacing position in which they are spaced by a shorter distance; and a controller for controlling the changing mechanism such that in a period after the sheet passes through the fixing nip and before a next sheet reaches the fixing nip, the rollers are brought into the first spacing position when the period is longer than a first predetermined period, and that the rollers are brought into the second spacing position when the period is shorter than the first predetermined period and is longer than a second predetermined period.