A buffer device stores, in relation to a first area and a second area, which are partial areas respectively located on an identical line of an encoding target frame, and a third area, which is a partial area on the line below the identical line, reference image data for each search range of a reference frame that is referred to during motion search processing executed in order of the first area, the second area, and the third area, the buffer device including a memory for storing the reference image data, and a buffer control unit which, when the motion search processing is executed on the second area, executes control so that among the reference image data included in a first search range that is referred to during the motion search processing of the first area, the reference image data included in a third search range that is referred to during the motion search processing of the third area are left in the memory without being deleted.