A deblocking filter, an image encoder, and an image decoder perform edge-filtering of moving-image data which can be divided into blocks, on groups of a predetermined number of pixels arrayed across edges between the blocks, and include: a processing unit concurrently performing column-direction-edge filtering on more than one first group of pixels which are arrayed in rows across ones of the edges oriented in a column direction, the ones of the edges belonging to a macroblock to be currently processed; and an rearrangement unit rearranging pixels being included in the more than one first group of pixels and the macroblock and having been processed by the processing unit, into more than one second group of pixels in respective columns.