According to one embodiment, a semiconductor storage device comprises a main memory, a request issue module, a delay module, and an access module. The main memory is configured to store candidate information for determining a compaction candidate for a nonvolatile memory. The request issue module is configured to issue an access request for the candidate information in the main memory. The delay module is configured to delay the access request issued from the request issue module. The access module is configured to access the candidate information in the main memory based on an access request delayed by the delay module.