1. A method for displaying screen information, the method comprising: storing a face image of a user to whom viewing a stereoscopic image is allowed; acquiring a face image of a viewer viewing the screen information; and displaying the screen information as a stereoscopic image or a planar image based on whether the face image of the viewer matches the face image of the user, wherein the screen information is displayed as the stereoscopic image when the face image of the viewer matches the face image of the user, and the screen information is displayed as the planar image when the face image of the viewer does not match the face image of the user.