The invention provides an image forming apparatus and a method for controlling the image forming apparatus. The image forming apparatus has a control portion, a printing portion, a paper sheet cassette, a cassette sensor, and an operation display portion. The image forming apparatus detects that the paper sheet cassette has been drawn out and that the paper sheet cassette has been housed, and upon detecting either that the paper sheet cassette has been drawn out or that the paper sheet cassette has been housed, detects that a reference operation has been performed. When the reference operation has been performed in a time period other than while a printing job is being executed, the control portion performs control so that the screen related to paper sheet setting is displayed, and when the reference operation has been performed while the printing job is being executed, the control portion performs control so that the screen related to paper sheet setting is not displayed.