To provide an accessing device which allows reliable protection of important data. A memory accessing device has a file system device which manages a logical memory space and a driver device which maintains a correlation information between the logical memory space and a physical memory space and which physically accesses a flash memory based on the correlation information. The flash memory is physically divided into a plurality of strings. The file system device manages the memory space by dividing the memory space into a plurality of partitions each of which is set to one of RO and RW. The driver device specifies a permission type to write the data in a string by correlating each string to a single logical partition.