An image forming apparatus includes a transfer portion, a fixing unit, a conveyance belt configured to convey a sheet from the transfer portion toward the fixing unit, a driving portion configured to drive the conveyance belt, and a controller configured to control the driving portion. The controller is configured to, in a case of switching the image forming apparatus to a standby state in which the image forming apparatus is ready to start an image forming operation and stands by for input of an image forming job, execute preheating in which the fixing unit is preliminarily heated, and cause the driving portion to rotate the conveyance belt while the preheating is executed.