1. An image converting device comprising: a downscaling unit which downscales a two-dimensional image to generate at least one downscaling image; a feature map generating unit which extracts feature information from the downscaling image to generate a feature map; a visual attention calculating unit which generates a low-level attention map based on visual attention of the feature map; and an image expansion unit which up-scales the low-level attention map, wherein an increasing gray value is added to image data disposed on an upper portion of the low-level attention map, and 0 or a decreasing gray value is added to image data disposed on a lower portion of the low-level attention map.