An apparatus for decoding video data receives a bitstream including a coding tree unit (CTU) of encoded video data and split information related to the CTU of the video data, determines a coding block to be decoded, determines a prediction partition mode for the coding block corresponding to the leaf node of the tree split structure among a plurality of prediction partition modes using mode type information included in the bitstream, the plurality of prediction partition modes including at least one prediction partition mode allowing the coding block to be predicted by being split into two equal-sized triangles of the same size, and decodes the coding block corresponding to the leaf node according to the determined prediction partition mode.