1. A video coding apparatus comprising: a motion vector detector configured to detect a first motion vector from a first reference image for a coding target block; a reference image composition unit configured to create a composite reference block that a first reference block of a specific region having a size equal to the coding target block or larger, the first reference block having been extracted from the first reference image using the first motion vector, has been composited with a predetermined region of at least one of other reference images; a motion compensated prediction unit configured to detect a second motion vector corresponding to the coding target block for the composite reference block by searching the specific region in the composite reference block, extract a block of the same size as the coding target block from the composite reference block using the second motion vector, and set the extracted block as a prediction block; and a coding unit configured to code a prediction difference block that the prediction block has been subtracted from the coding target block, and the second motion vector.