This invention relates to an image forming apparatus that can correct a curl of a transfer medium correctly and smoothly. This image forming apparatus includes a curl correcting mechanism, including a rotatable sponge roller and a fixed press member which presses the sponge roller while biting into part of the outer surface of the sponge roller, and provided downstream of a fixing processing unit, and a regulating unit, provided immediately before the curl correcting means, so as to guide the leading end of the transfer medium to that position on the outer surface of the sponge roller which is tilted, within the range of 5° to 10° (both inclusive) from a reference line that connects the center of the sponge roller and the press start position of the press member with respect to the sponge roller, to a direction opposite to the rotating direction of the sponge roller.