Provided is a data processor for generating three-dimensional image data from two-dimensional original image data, the three-dimensional image data including depth value, the apparatus comprising: a first clustering processor for dividing the two-dimensional original image data into a first plurality of clusters based on brightness; a three-dimensional data generating unit for setting a predetermined direction as a brighter-to-darker direction, and for generating information, as first depth information, such that depth value for a first cluster among the plurality of clusters is set to be larger than depth value for a second cluster which neighbors the first cluster and is located nearer to a starting point of the brighter-to-darker direction than the first cluster where the brightness of the first cluster is darker than the brightness of the second cluster.