1. An apparatus for overlaying a plurality of images comprising: a broadcast image layer generator configured to generate a broadcast image layer based on a received broadcast signal; an application image layer generator configured to generate an application image layer based on an application image; and an overlay processor configured to generate an overlay image obtained by overlaying the broadcast image layer with the application image layer, so that a broadcast image corresponding to the broadcast image layer and an application image corresponding to the application image layer may be displayed simultaneously on a screen.