A region determination circuit determines, for a first block encoded by referring to a first prediction block generated by applying a bidirectional prediction mode for a first component of a pixel value from among blocks in a coding-target picture included in video data, a partial region to which a unidirectional prediction mode is to be applied for a second component on the basis of a difference value for the first component between corresponding pixels belonging to the first prediction block and the first block. A prediction circuit generates a second prediction block for the second component by applying a unidirectional prediction mode to the partial region and a bidirectional prediction mode to a region that is not the partial region. An encoder calculates a prediction error for the second component between corresponding pixels belonging to the first block and the second prediction block and encodes the prediction error.