Abstract: A convolutional coding unit generates transmission data by performing an error correcting code process for sending data. A mapping unit arranges the transmission data at signal points corresponding to the data value. A PN sequence generating unit generates a PN sequence based on part of the transmission data. A spreading unit spreads a transmission signal by multiplying an output of the mapping unit by the PN sequence generated with the PN sequence generating unit. A despreading unit detects the PN sequence used on a transmitting side, and despreads the received signal by using the detected PN sequence. A remapping unit obtains the transmission data from the signal points at which the received signal is arranged. A supplementary information processing unit obtains supplementary information based on the detected PN sequence. A Viterbi decoding unit regenerates the sending data from the transmission data by using the supplementary information.