1. An apparatus for outputting an image using a plurality of chroma-key colors, the apparatus comprising: a microprocessor unit (MPU) that applies at least two chroma-key colors to one boundary of an area included in a foreground image, and represents the size of the area adjacent to the chroma-key colors to set a block for the area; and a video controller that makes the block set by the MPU transparent to display an area of a background image covered by the foreground image, which overlaps the block.