A reconstructed block creating method is provided which includes decoding an intra prediction mode using an intra prediction mode group indicator and a prediction mode index, constructing a prediction block, inversely quantizing a received residual signal using a quantization parameter and adaptively inversely transforming the residual signal using the intra prediction mode to create a residual block, and adding the prediction block and the residual block to create a reconstructed block. The quantization parameter is reconstructed using a minimum quantization CU size, and the minimum quantization CU size is determined by a parameter transmitted from a picture parameter set. Therefore, it is possible to improve image quality by adaptively adjusting a quantization parameter of a current block depending on the size of a coding unit and enhance compression efficiency of an image by effectively encoding/decoding the quantization parameter.