An image forming apparatus in which time taken before a screen is displayed after return from sleep is reduced. Image data to be displayed on an LCD touch panel after the image forming apparatus returns from a power saving state to a normal state is generated when the image forming apparatus shifts from the normal state to the power saving state. The generated image data is stored in a memory. When the image forming apparatus returns from the power saving state to the normal state, the LCD touch panel is caused to display an image represented by the image data stored in the memory.