An image forming apparatus includes: an image forming unit configured to form images based on image data transmitted from information processing apparatus of users including registered users and unregistered users; a setting unit configured to set permission information for each user based on a log of the image forming and limit information; a first judging unit configured to determine whether user identification information is attached to image data; a second judging unit configured to determine, based on the permission information that is set for an unregistered user, whether to permit execution of image forming of the image data, when the first judging unit determines that the user identification information is not attached to the image data.