A video encoding/decoding apparatus includes: a video encoder for dividing coding unit block into combination of subblocks of codable size, determining combination of inter blocks and intra blocks with respect to each subblock, determining encoding order of intra encoding blocks within coding unit considering referencing possibility of peripheral pixel values of current block to be intra-prediction encoded, bi-directional intra prediction encoding the current block in determined encoding order, and transmitting encoding mode/size information of subblocks after locating encoding mode/size information in front of a syntax of the coding unit; and a video decoder for restoring encoding mode/size information of subblocks within the coding unit by decoding encoded data, reconstructing inter prediction encoded blocks, based on restored encoding mode information, and determining decoding order of intra prediction mode blocks according to encoding mode/size information of each subblock within coding unit, and conditions on referencing possibility of peripheral blocks of coding unit.