According to an embodiment, a decoding device includes a variable node processor, a check node processor, a first forwarder, and a second forwarder. The variable node processor is configured to perform variable node processing on variable nodes defined by a code and output first messages. The check node processor is configured to perform check node processing on check nodes defined by the code based on the first messages and output second messages. The first forwarder is configured to forward one or more first messages remaining after excluding messages to be forwarded to one or more check nodes corresponding to one or more of the second messages having been stored in ae storage, to the check nodes. The second forwarder is configured to forward the second messages to the variable nodes and forward the one or more of the second messages to the storage.