Disclosed are a method of encoding a division block in video encoding and a method of decoding a division block in video decoding. An input picture is divided into encoding unit blocks. The coding unit (CU) blocks are divided into sub-CU blocks. The sub-CU blocks are encoded by selectively using at least one of intra prediction encoding and inter prediction encoding. A decoding process is performed through a reverse process of the encoding method. When pixel values of a CU block are encoded in video encoding, the flexibility in selecting an encoding mode is increased and the efficiency of encoding is increased.