To provide an error-correction device which hardly deteriorates in redundancy, even if multivalued under is small.

An error-correction device is equipped with an encoder and a decoder which correct errors by block units, a block generator which divides input data into D bits and replaces the residual bits with specific data to generate a block, a symbol generator which generates data of divided D bits for a data block outputted from the encoder and symbol data, by dividing a parity block into D bits, a binary/multivalued converter which converts the generated symbol data into multivalued signals, a multivalued/binary converter which converts the multivalued signals into binary signals, a block regenerator which adds specific data to the converted data symbol or continuously connects data of D bits to the parity symbol to regenerate a block, and a data generator which outputs the D-bit data from a block.