A method and apparatus for generating a thumbnail in a size requested by an application at high definition and high speed to browse a digital image are provided. An original image is partially decoded to generate a first thumbnail and the first thumbnail is partially decoded to generate a second thumbnail in a size requested by an application. Accordingly, a digital image is displayed on a full screen using a stored thumbnail instead of decoding an original image, and therefore, a large-capacity high-definition image can be displayed quickly. In addition, to display a thumbnail in various sizes, a small size of the thumbnail is not enlarged but the thumbnail having a size approximate to a full screen size is reduced. Accordingly, degradation of picture quality is decreased.