An encoding device includes a determination unit configured to determine, when performing detection of a motion vector using the decoded image of a frame image encoded in increments of blocks prior to the frame image to be encoded regarding an encoded block to be encoded of a plurality of blocks included in this frame image to be encoded at the time of encoding a frame image included in a moving image where a first image and a second image are arrayed using inter-image prediction encoding processing, correlation height as to the image of the encoded block regarding each of the image of a first area corresponding to the first image and the image of a second area corresponding to the second image included in a boundary block straddling a boundary between the first image and the second image of a block included in the decoded image.