An image forming apparatus comprising: an image forming section which forms an image on a sheet material; a curl correcting mechanism which interposes and conveys the sheet material on which the image has been formed by the image forming section. Pressure applied to one surface of the sheet material during an interposing operation and a conveying speed of the sheet material can be changed, the curl correcting mechanism changes the conveying speed from an initial speed vs to a target speed vo higher than the initial speed (vo>vs) while the sheet material is pressed, and the curl correcting mechanism changes the pressure to a high pressure in response to a change of the conveying speed, whereby a curl of the sheet material is reduced.