To easily and quickly process BAS coding with software by obtaining a transmission BAS error correction bit by referring to a table.

When a transmission BAS inputting part 101 judges that a transmission BAS code inputted from an H.221 multiplexing part 110 is received, the transmission BAS inputting part 101 outputs the inputted transmission BAS code as it is to a matrix arithmetic part 102 and a parity inserting part 104. The matrix arithmetic part 102 calculates the multiplied result of the transmission BAS code inputted from the transmission BAS inputting part 101 and an inspection symbol generation matrix, by referring to a BAS-error correction bit calculation table stored in a memory 103. The matrix arithmetic part 102 outputs an obtained vector to a parity inserting part 104 as a transmission BAS-error correction bit. Then, the parity inserting part 104 inserts the transmission BAS-error correction bit applied from the matrix arithmetic part 102 into the transmission BAS-code, and outputs it with respect to a line interface part 120.