Method and device for synchronizing reference image and supplementary image in real-time broadcast program. The present invention provides a synchronization method for: calculating a time difference between a current frame of a reference image and a reference time stamp on the basis of the reference time stamp, which is contained in a program level descriptor and indicates a start time of a frame regarding a reference image; and adjusting synchronization between the frame regarding the reference image and a frame regarding a supplementary image by using the time difference. Since synchronous time information is signaled together with a stream delivered in real time, synchronization between a stored supplementary image and a reference image transmitted in real time is enabled even though a first PMT of a time when a stereoscopic video service is started is not received or a packet error is generated. Thus, the invention can provide a stable stereoscopic image service