To eliminate the need for buffering in order to calculate data length information on data as an object of computation, a first exclusive-OR unit 53 executes computation of exclusive-OR of a cyclic code R(x) of the integral multiple bit bits block A(x) and a data string of M bits, containing the fraction bits block B(x). A first shifting unit 54 shifts the exclusive-OR of the cyclic code R(x) and the data string of M bits, containing the fraction bits block B(x), by {M−H(k)} bits toward a least significant side, where M is a parallel width and H(k) is a bit length of the fraction bits block B(x). An R′(x) generation unit 55 generates a cyclic code R′(x) that is a cyclic code of the data after shifting. To obtain R″(x), a second shifting unit 56 shifts the cyclic code R(x) by H(k) bits toward a most significant side. A second exclusive-OR unit 57 executes computation of exclusive-OR of the cyclic code R′(x) and data R″(x).