Provided are a user interfacing display apparatus having improved operability without confusing the user as to setting displayed on a pop-up screen, and an image forming apparatus. When a copy ratio key as a detail setting key is selected on an LCD as a display section provided in the user interfacing display apparatus mounted on an image forming apparatus, the pop-up screen is displayed. At the same time, a display state of an interruption key is changed, so as to be displayed to inform that the interruption key is unavailable. While the pop-up screen is being displayed, a user is not allowed to select the interruption key. Thus, for example, on contrary to a case where process is switched to an interruption mode while the pop-up screen is being displayed, there will be no confusion as to the detail setting displayed on the pop-up screen before switching to the interruption mode.