The present disclosure concerns a method and apparatus for selecting an intra prediction mode and a video encoding/decoding method and apparatus using same. The encoding apparatus selects an intra prediction mode of current block to encode from input video by a variation of the value of pixel adjacent to the current block; encodes a residual block from intra-predicting the current block in the selected intra prediction mode of current block to generate coded coefficient bit having a bitstream generator for generating and outputting a bitstream including the coded coefficient bit and a prediction mode bit representing the selected intra prediction mode of current block by a macroblock or subblock unit with the prediction mode bit included selectively in the bitstream depending on the variation. Accordingly, selection process of a prediction mode for image compression is simplified, a faster compression is obtained and compressed data is deflated to improve compression efficiency.