According to embodiments, an error correction decoder carrying out iterative decoding for coded data based on LDPC code. The decoder comprises a generation unit and an inversion, control unit. The generation unit is configured to generate an inversion node list listing variable nodes connected to check nodes not satisfying a parity check when a code word cannot be obtained after carrying out the iterative decoding a first number of iterations. The inversion control unit is configured to choose a variable node which is a target for inversion from among the variable nodes listed in the inversion node list, and to carry out inversion processing which includes updating an input likelihood of the variable node which is the target for inversion temporarily by inverting a sign of an a posteriori likelihood of the variable node which is the target for inversion.