An apparatus for encoding images includes: a predictor to determine a prediction unit (PU) mode among a plurality of PU modes indicating types of partition of a current coding unit (CU) into one or more prediction units (PUs), and generate a predicted block of the current CU by performing an intra prediction or an inter prediction for each PU of the determined PU mode, wherein a size of the current CU is 2N×2N, and the plurality of PU modes includes 2N×hN or hN×2N PU mode in which the current CU is partitioned into PUs respectively having a size of 2N×hN or hN×2N, h being a fractional number smaller than 1; a subtractor to subtract the predicted block from the current CU to generate a residual block; a transformer to transform the residual block into a frequency domain to generate a frequency one or more transform blocks.