Provided are a method and a device for encoding a video to improve an intra prediction processing speed, and a method and a device for decoding the video. The method for encoding a video performs parallel intra prediction and includes: obtaining, by using pixels of peripheral blocks processed prior to a plurality of adjacent blocks, reference pixels used for intra prediction of each of the plurality of adjacent blocks; performing, by using the obtained reference pixels, intra prediction in parallel for each of the plurality of adjacent blocks; and adding reference pixel syntax information to a bitstream.