Provided is a radio communication apparatus capable of always obtaining the optimum error rate characteristic when an LDPC code is used for an error-correcting code. In the apparatus, a temporary bit insertion section (101) inserts a temporary bit into a position equivalent to that of the systematic bit corresponding to a variable node having the largest number of connections with a check node in the Tanner graph corresponding to a check matrix in a transmission bit string and outputs the generated bit string to an LDPC coding section (102), The LDPC coding section (102) performs LDPC coding on the bit string inputted from the temporary bit insertion section (101) by using the check matrix and obtains an LDPC code word composed of the systematic bit and a parity bit. The LDPC code word is outputted to a temporary bit removal section (103).