1. A soft output decoder that receives code words corresponding to a plurality of information words and calculates soft decision decoding results of the plurality of information words from a plurality of likelihood values corresponding to a plurality of candidate values adopted by the plurality of information words, the soft output decoder comprising: a hard decision decoder that decides one of the plurality of candidate values as an estimated value; and a likelihood calculator that bans calculation of a likelihood value corresponding to the estimated value and calculates other likelihood values corresponding to others of the plurality of candidate values in the plurality of likelihood values.