The image forming apparatus has a discharge device, an air blow device and a detection device, wherein an amount of blown air by the air blow device when the height of the recording materials detected by the detection device is higher than a preset first detection position is smaller than an amount of blown air by the air blow device when the detected height of the recording materials is lower than the first detection position. Thereby, there is provided an image forming apparatus which is improved in the alignment of the recording materials on the stacking portion.