To protect data just before reloading and to shorten time required for data reloading of a sector even when an accident occurs in the middle of reloading.

This device has a non-volatile memory 1 having plural sectors and capable of electric erasure and write for performing the erasure for the unit of a sector, a non-volatile memory control means 2 for instructing and controlling the erasure, write and read of data to the non-volatile memory 1, a temporary sector data holding means 3 for temporarily holding sector data and a sector managing information holding means 10 for holding sector managing information showing which sector stores effective data.