A coding apparatus for coding a frame of a moving image on a block basis includes a calculation unit configured to, for a block adjoining the target block and having a motion vector to be used for coding having been selected, from among blocks in the frame, calculate a difference between a detected motion vector and a motion vector of the target block and calculate a difference between pixels of a reference block identified by applying a motion vector of the adjoining block to the target block and pixels of the target block, a determination unit configured to determine whether a motion vector to be used for coding the adjoining block has been detected at the time of processing, and a motion vector selection unit configured to, based on a calculation result and a determination result, select a motion vector to be used for coding the target block.