In an image forming apparatus in which a scanner portion is disposed in an upper portion of the apparatus, a paper cassette is disposed in a lower portion of the apparatus, and a print portion is disposed between the scanner portion and the paper cassette, in one embodiment, a paper post-processing portion that performs paper post-processing for paper transported from the apparatus main body after printing is disposed in a space of the apparatus main body formed by the scanner portion, the print portion, and the paper cassette. Provided in a discharge roller portion that discharges paper from the paper post-processing portion to a discharge tray are a drive roller, and a first idler roller and second idler roller that form a pair with the drive roller and can be selectively used when discharging paper to the discharge tray.