A belief propagation decoding method using a parity check matrix for decoding of a transmission information sequence coded by a low density parity check convolutional code, LDPC-CC, the method comprising: a log-likelihood ratio initialization step of setting initial values of log-likelihood ratios, a sequence of row process calculating steps of updating the log-likelihood ratios in a submatrix of the parity check matrix; a sequence of column process calculating steps of updating the log-likelihood ratios in a submatrix of the parity check matrix; and wherein the sequence of the row process calculating steps and the sequence of the column process calculating steps are performed alternately until a final iterative calculation, the parity check matrix is composed of submatrixes P1 on a main diagonal, submatrixes P2 on a below diagonal adjacent to the main diagonal, and zero submatrixes in all other diagonals: P 1 0 ⋯ 0 P 2 P 1 ⋯ 0... ⋮ ⋱ ⋮ 0 0 ⋯ P 1, in the sequence of the row process calculating steps, the submatrix for the first step is composed of a first submatrix P1 and a first submatrix P2 along said diagonals, and the submatrix for i-th subsequent said row process calculating steps is composed of (i-1)-th submatrix P2, i-th submatrix P1 and i-th submatrix P2, where i is a natural number larger than 1; in the sequence of the column process calculating steps, the submatrix for the first step is composed of the first submatrix P1 and the first submatrix P2 along said diagonals, and the submatrix for i-th subsequent said column process calculating steps is composed of (i-1)-th submatrix P1, (i-1)-th submatrix P2, i-th submatrix P1 and i-th submatrix P2; and an estimating step of estimating a codeword using the updated log-likelihood ratios after the final iterative calculation. a log-likelihood ratio initialization step of setting initial values of log-likelihood ratios, a sequence of row process calculating steps of updating the log-likelihood ratios in a submatrix of the parity check matrix; a sequence of column process calculating steps of updating the log-likelihood ratios in a submatrix of the parity check matrix; and wherein the sequence of the row process calculating steps and the sequence of the column process calculating steps are performed alternately until a final iterative calculation, the parity check matrix is composed of submatrixes P1 on a main diagonal, submatrixes P2 on a below diagonal adjacent to the main diagonal, and zero submatrixes in all other diagonals: P 1 0 ⋯ 0 P 2 P 1 ⋯ 0... ⋮ ⋱ ⋮ 0 0 ⋯ P 1, in the sequence of the row process calculating steps, the submatrix for the first step is composed of a first submatrix P1 and a first submatrix P2 along said diagonals, and the submatrix for i-th subsequent said row process calculating steps is composed of (i-1)-th submatrix P2, i-th submatrix P1 and i-th submatrix P2, where i is a natural number larger than 1; in the sequence of the column process calculating steps, the submatrix for the first step is composed of the first submatrix P1 and the first submatrix P2 along said diagonals, and the submatrix for i-th subsequent said column process calculating steps is composed of (i-1)-th submatrix P1, (i-1)-th submatrix P2, i-th submatrix P1 and i-th submatrix P2; and an estimating step of estimating a codeword using the updated log-likelihood ratios after the final iterative calculation.