1. A semiconductor storage device comprising: a first memory area configured in a volatile semiconductor memory which performs writing of data by a first unit or less, the first unit being an access unit to the semiconductor storage device; second and third memory areas configured in a nonvolatile semiconductor memory which performs writing of data by a second unit and performs erasing of data by a third unit, the third unit being twice or larger natural number times as large as the second unit; and a controller executing: a first processing for storing a plurality of data by the first unit in the first memory area; a second processing for storing data outputted from the first memory area by a first management unit in the second memory area, the first management unit being twice or larger natural number times as large as the first unit and being less than the third unit; and a third processing for storing data outputted from the first memory area by a second management unit in the third memory area, the second management unit being twice or larger natural number times as large as the first management unit.