According to an embodiment, a decoding apparatus for a low-density parity-check (LDPC) code includes a first calculator, a second calculator, and a selector. The first calculator is configured to perform row processing based on a first decoding algorithm. The second calculator is configured to perform row processing based on a second decoding algorithm having a lower error correction capacity than that of the first decoding algorithm. The selector is configured to select an output value from the row processing performed by the second calculator when an error in an output value from the row processing performed by the first calculator is greater than an error in the output value from the row processing performed by the second calculator.