A semiconductor storage device includes a first memory area configured in a volatile semiconductor memory, second, third, and fourth memory areas configured in a nonvolatile semiconductor memory, and a controller which executes following processing. The controller executes a first processing for storing a plurality of data by the first unit in the first memory area, a second processing for storing data by a first management unit in the fourth memory area, a third processing for storing data by a second management unit in the third memory area, a fourth processing for moving an area of the third unit having the oldest allocation order in the fourth memory area to the second memory area, and a fifth processing for selecting data in the second memory area and copying the selected data to an empty area of the third unit in the second memory area.