performs conversion into a converted soft decision signal capable of expressing a white circle position in the lower stage in fig2 that shows that the distance between two symbols corresponds to an intermediate value of the symbols for example namely in this case the distance between two symbols can be expressed by one or zero bit thus the conversion processing circuit 17 changes the quantization level of the soft decision signal according to the reliability in other words the conversion processing circuit 17 performs processing so that the higher the reliability is the more finely the quantization level is set and the lower the reliability is the more roughly the quantization level is set accordingly the converted soft decision signal converted by the conversion processing circuit 17 comes close to the intermediate value between two symbols when the reliability is low thus in this embodiment the conversion processing circuit 17 generates a converted soft decision signal in which the number of bits of the soft decision signal is reduced when the reliability is low this enables a reduction in memory capacity to be used in deinterleaving of the deinterleave circuit 18 as described later however in consideration of actual hardware mounting when information with high reliability is continued the number of bits of the soft decision signal cannot be reduced for this reason the reliability information is converted into a variable length code thereby making it possible to reduce the number of bits namely the conversion processing circuit 17 expresses the reliability information by a small number of bits when the reliability is high and expresses it by a large number of bits when the reliability is low this makes it possible.