An image forming apparatus includes an image forming unit, a first sheet stack portion, a sheet output section, and a post processing unit. The image forming unit forms an image on a sheet. The first sheet stack portion is provided at an upper face of the image forming unit. The sheet output section outputs the sheet on which the image is formed by the image forming unit from one side of the image forming apparatus to the first sheet stack portion. The post processing unit is provided adjacent to a lateral side of the image forming unit at an upstream side of the sheet output section to execute post processing on the sheet. A sheet subjected to post-processing by the post-processing unit is output to the first sheet stack portion from the same direction as a sheet not subjected to post-processing by the post-processing unit.