An image forming apparatus is composed of a main body, an image forming portion provided in the main body to form an image on a sheet, a top receiving tray provided on a top of the main body to load the sheet on which the image is formed in the image forming portion so as to be visible from the top of the main body, a side receiving tray provided at a side of the main body and under the top receiving tray to load the sheet on which the image is formed in the image forming portion with a maximum sheet loading amount more than the top receiving tray, and a control unit to control to select one of the top receiving tray and the side receiving tray as a discharge destination for the sheet according to whether or not a number of the output sheets outputted from the image forming portion exceeds a prescribed threshold value.