The present invention provides a method of scaling a partial area of a main picture, by which the partial area of the main picture can be magnified in a manner of scaling the partial area of the picture displayed on a screen like using a virtual magnifier without employing a separate expensive hardware resource. The present invention comprises a first step of making a main scaler extract image data of the partial area to be scaled from full image data according to prescribed scaling information including magnification/reduction information for the partial area of a display picture, a second step of making a sub-scaler scale the extracted image data of the partial area at a prescribed rate, and a third step of overlaying the scaled image data of the partial area on the full image data provided from the main scaler.