A memory controller according to an embodiment includes a first decoder which calculates first extrinsic value based on a decoding success rate specified using a first table showing a correspondence between first distance information indicating a square Euclidean distance between a first decode word and a first soft input value and a first decoding success rate indicating a probability of a decoding result that the first decode word is correct, and a second decoder which calculates second extrinsic value based on a decoding success rate specified using the second table showing a correspondence second distance information indicating a square Euclidean distance between a second decode word and a second soft input value and a second decoding success rate indicating a probability of a decoding result that the second decode word is correct.