An encoding method comprising the steps of: supplying three different parity check polynomials for creating a Low-Density Parity-Check Convolutional Code of a time-variant period of 3, the Low-Density Parity-Check Convolutional Code created by using a parity check matrix in which three check equations are arranged repeatedly; selecting, by a processor, a parity check polynomial from among the three different parity check polynomials; and applying, by a processor, the selected parity check polynomial to generate a low-density parity-Check convolutional code, characterized in that: the three different parity check polynomials are respectively represented by following three Equations; ∑ j = 1 n − 1 D a # 1, j, 1 + D a # 1, j, 2 + D a # 1, j, 3 X j D + D b # 1,1 + D b # 1,2 + D b # 1,3 P D = 0 ∑ j = 1 n − 1 D a # 2, j, 1 + D a # 2, j, 2 + D a # 2, j, 3 X j D + D b # 2,1 + D b # 2,2 + D b # 2,3 P D = 0 ∑ j = 1 n − 1 D a # 3, j, 1 + D a # 3, j, 2 + D a # 3, j, 3 X j D + D b # 3,1 + D b # 3,2 + D b # 3,3 P D = 0 wherein: D is a delay operator; X j is a polynomial representation of an information sequence X j that is a target to be encoded where j is each integer of one or more, and n-1 or less, where n is an integer of 2 or more; P is a polynomial representation of a parity sequence; a #k,j,1, a #k,j,2 and a #k,j,3 are parameters, where k designates each of 1, 2 and 3, and j designates each integer of one or more, and n-1 or less, a #k,j,1, a #k,j,2 and a #k,j,3 are integers of zero or more, where a #k,j,1 ≠ a #k,j,2 ≠ a #k,j,3, b #k,1, b #k,2 and b #k,3 are parameters, where k designates each of 1, 2 and 3, b #k,1 and b #k,2 are natural numbers, where b #k,1 ≠ b #k,2 ≠ b #k,3, and a #k,j,3 is equal to zero in each of the three different parity check polynomials and/or b #k,3 is equal to zero in each of the three different parity check polynomials. supplying three different parity check polynomials for creating a Low-Density Parity-Check Convolutional Code of a time-variant period of 3, the Low-Density Parity-Check Convolutional Code created by using a parity check matrix in which three check equations are arranged repeatedly; selecting, by a processor, a parity check polynomial from among the three different parity check polynomials; and applying, by a processor, the selected parity check polynomial to generate a low-density parity-Check convolutional code, characterized in that: the three different parity check polynomials are respectively represented by following three Equations; ∑ j = 1 n − 1 D a # 1, j, 1 + D a # 1, j, 2 + D a # 1, j, 3 X j D + D b # 1,1 + D b # 1,2 + D b # 1,3 P D = 0 ∑ j = 1 n − 1 D a # 2, j, 1 + D a # 2, j, 2 + D a # 2, j, 3 X j D + D b # 2,1 + D b # 2,2 + D b # 2,3 P D = 0 ∑ j = 1 n − 1 D a # 3, j, 1 + D a # 3, j, 2 + D a # 3, j, 3 X j D + D b # 3,1 + D b # 3,2 + D b # 3,3 P D = 0 wherein: D is a delay operator; X j is a polynomial representation of an information sequence X j that is a target to be encoded where j is each integer of one or more, and n-1 or less, where n is an integer of 2 or more; P is a polynomial representation of a parity sequence; a #k,j,1, a #k,j,2 and a #k,j,3 are parameters, where k designates each of 1, 2 and 3, and j designates each integer of one or more, and n-1 or less, a #k,j,1, a #k,j,2 and a #k,j,3 are integers of zero or more, where a #k,j,1 ≠ a #k,j,2 ≠ a #k,j,3, b #k,1, b #k,2 and b #k,3 are parameters, where k designates each of 1, 2 and 3, b #k,1 and b #k,2 are natural numbers, where b #k,1 ≠ b #k,2 ≠ b #k,3, and a #k,j,3 is equal to zero in each of the three different parity check polynomials and/or b #k,3 is equal to zero in each of the three different parity check polynomials. D is a delay operator; X j is a polynomial representation of an information sequence X j that is a target to be encoded where j is each integer of one or more, and n-1 or less, where n is an integer of 2 or more; P is a polynomial representation of a parity sequence; a #k,j,1, a #k,j,2 and a #k,j,3 are parameters, where k designates each of 1, 2 and 3, and j designates each integer of one or more, and n-1 or less, a #k,j,1, a #k,j,2 and a #k,j,3 are integers of zero or more, where a #k,j,1 ≠ a #k,j,2 ≠ a #k,j,3, b #k,1, b #k,2 and b #k,3 are parameters, where k designates each of 1, 2 and 3, b #k,1 and b #k,2 are natural numbers, where b #k,1 ≠ b #k,2 ≠ b #k,3, and a #k,j,3 is equal to zero in each of the three different parity check polynomials and/or b #k,3 is equal to zero in each of the three different parity check polynomials. a #k,j,1, a #k,j,2 and a #k,j,3 are parameters, where k designates each of 1, 2 and 3, and j designates each integer of one or more, and n-1 or less, a #k,j,1, a #k,j,2 and a #k,j,3 are integers of zero or more, where a #k,j,1 ≠ a #k,j,2 ≠ a #k,j,3, b #k,1, b #k,2 and b #k,3 are parameters, where k designates each of 1, 2 and 3, b #k,1 and b #k,2 are natural numbers, where b #k,1 ≠ b #k,2 ≠ b #k,3, and a #k,j,3 is equal to zero in each of the three different parity check polynomials and/or b #k,3 is equal to zero in each of the three different parity check polynomials.