STORAGE DEVICE AND STORAGE METHOD

PROBLEM TO BE SOLVED: To improve reliability by preventing data from being lost even when a power accumulated in an accumulator is not sufficient.SOLUTION: When receiving a writing instruction from a host device 10, an access control circuit 108 (a writing control part) makes a cache memory 103 (a non-volatile storage part) store designated data. When the amounts of data which have not been stored in a flash memory 102 among the data stored in the cache memory 103 are larger than a threshold determined in accordance with the residual amounts of a power accumulated in a battery unit 115 (an accumulator), the access control circuit 108 (a saving control part) makes the flash memory 102 store the data which have been stored in the cache memory 103, and which have not been stored in the flash memory 102.