1. A decoding device for decoding LDPC (Low Density Parity Check) codes, comprising: message calculation means for performing a variable node calculation for decoding said LPDC codes using a message to be supplied, or performing a check node calculation, and outputting the message to be obtained as a result of said calculation; storing means for storing said message; and control means for performing writing control for writing the message that said message calculation means output in said storing means, and readout control for reading out the same message to be employed for the calculation of said message calculation means from said storing means twice, and supplying these to said message calculation means.