1. An ROI (region of interest) information setting method for scalable video, the method comprising: setting at least one ROI in a frame, and allocating ROI identification number to the each of at least one ROI; mapping the ROI identification number to a layer identification number; and mapping at least one or more slice identification numbers to the layer identification number, wherein an SEI (supplemental enhancement information) message comprises mapping information between the ROI identification number to the layer identification number and mapping information between the ROI identification number and the at least one or more slice identification numbers.