A decoding method for decoding a bit stream corresponding to a target B-picture of plural pictures constituting a moving image, including: a decoding step of, when decoding a target B-picture to be decoded, receiving first coded data in the bit stream and decoding each block in the target B-picture in one decoding mode among I mode decoding, in which a block in the target B-picture is decoded without referring to other pictures, P mode decoding, in which a block in the target B-picture is predictively decoded with reference to one already-decoded picture, and B mode decoding in which a block in the target B-picture is predictively decoded with reference to two already-decoded pictures to recover each block in the target B-picture, characterized by a candidate picture information decoding step of receiving second coded data in the bit stream and decoding information, which indicates whether or not the target B-picture is a candidate for a reference picture at decoding a picture that follows the target B-picture, to obtain information indicating that the target B-picture is a candidate for a reference picture or information indicating that the target B-picture is not a candidate for a reference picture, a reference picture information decoding step of receiving third coded data in the bit stream and in the P mode decoding in which a block in the target B-picture is predictively decoded, determining, as a reference picture, one picture among already-decoded pictures, each of which is indicated to be a candidate for a reference picture, and in the B mode decoding in which a block in the target B-picture is predictively decoded, determining, as a reference picture, two pictures among already-decoded pictures, each of which is indicated to be a candidate for a reference picture. a decoding step of, when decoding a target B-picture to be decoded, receiving first coded data in the bit stream and decoding each block in the target B-picture in one decoding mode among I mode decoding, in which a block in the target B-picture is decoded without referring to other pictures, P mode decoding, in which a block in the target B-picture is predictively decoded with reference to one already-decoded picture, and B mode decoding in which a block in the target B-picture is predictively decoded with reference to two already-decoded pictures to recover each block in the target B-picture, characterized by a candidate picture information decoding step of receiving second coded data in the bit stream and decoding information, which indicates whether or not the target B-picture is a candidate for a reference picture at decoding a picture that follows the target B-picture, to obtain information indicating that the target B-picture is a candidate for a reference picture or information indicating that the target B-picture is not a candidate for a reference picture, a reference picture information decoding step of receiving third coded data in the bit stream and in the P mode decoding in which a block in the target B-picture is predictively decoded, determining, as a reference picture, one picture among already-decoded pictures, each of which is indicated to be a candidate for a reference picture, and in the B mode decoding in which a block in the target B-picture is predictively decoded, determining, as a reference picture, two pictures among already-decoded pictures, each of which is indicated to be a candidate for a reference picture.