An image forming apparatus in which an image quality priority mode in which image density adjustment or image gradation control is effected to thereby give priority to the quality of an output image, and a speed priority mode in which gradation control is partly effected or is not effected to thereby output the output image within a short time can be selected by a user. A mode selection screen for selecting an image forming mode is displayed on the operating panel of the image forming apparatus. The image quality priority mode giving priority to the quality of image and the speed priority mode giving priority to speed are selectively displayed. When the user selects the image quality priority mode, and image control parameter is renewed immediately before image forming by image control, and the image forming is effected by the use of the renewed image control parameter, and when the speed priority mode is selected, at least part of the image control is not effected, but the image forming is effected.