A method of decoding an intra prediction mode, can include reconstructing an intra prediction mode group indicator and a prediction mode index; constructing an MPM group including three intra prediction modes using present intra prediction modes of left and top blocks of the current block; determining an intra prediction mode of the MPM group corresponding to the prediction mode index as the intra prediction mode of the current block when the intra prediction mode group indicator indicates the MPM group; and determining the intra prediction mode of the current block using the prediction mode index and the three intra prediction modes of the MPM group when the intra prediction mode group indicator does not indicate the MPM group, in which a DC mode and a planar mode are two non-directional intra prediction mode, and a mode number of the planar mode is lower than mode numbers of the other intra prediction modes.