A file to be read or written is designated and accessed from an access device side to a nonvolatile memory device. In an initialization after start-up of the power source, an empty capacity detector detects empty capacity parameters of a nonvolatile memory with dividing the memory into a plurality of regions. An empty capacity parameter notification part notifies the access device of the empty capacity parameters in a stepwise fashion whenever the empty capacity detector detects an empty capacity. With this, at the time when the empty capacity becomes not less than a capacity required to write file data, the data can be written to the nonvolatile memory without waiting for completion of the initialization, resulting in improvement of a response in the recording.