1. A method of transmitting stereoscopic video, comprising: generating a base image and an additional image using a left image and a right image; generating a base image stream, corresponding to the base image, and an additional image stream, corresponding to the additional image, by coding the base image and the additional image, respectively; generating single stream information by multiplexing the base image stream and the additional image stream; and transmitting image information including the single stream information, wherein the additional image includes a reduced left image corresponding to the left image and a reduced right image corresponding to the right image based on a predetermined image format.