1. A coding apparatus, comprising: a window information acquiring unit acquiring window information indicating an arrangement of windows on a screen that includes a plurality of windows; an identifying unit identifying one or more macroblocks that include a border between overlapping windows from the window information and macroblock information indicating an arrangement of macroblocks into which the screen is partitioned; a classifying unit partitioning each of the identified one or more macroblocks into sub-blocks so as to conform to the border and classifying the sub-blocks into which the one or more macroblocks are partitioned into groups based on whether or not the sub-blocks include the border; and a coding unit coding the sub-blocks classified into the groups by performing motion vector prediction using a certain sub-block in a group for sub-blocks classified in the same group and applying a result of the motion vector prediction of the certain sub-block to the other sub-blocks classified in the same group as the certain sub-block.