When carrying out an average prediction, an intra predictor carries out a filtering process on target pixels of the intra prediction located at an upper end and a left end of the block, the filtering process using an intermediate prediction value, which is an average value of adjacent pixels of the block, and at least one adjacent pixel of the target pixel. The intra predictor also sets a filter coefficient to ¾, associated with the intermediate prediction value for a target pixel at the upper end of the block other than the target pixel at an upper left corner of the block, and sets a filter coefficient to ¼, associated with the adjacent pixel adjacent to the upper side of the target pixel at the upper end of the block. As a result, prediction errors locally occurring can be reduced, and the image quality can be improved.