In the present invention, a vacant block which is unwritten is identified as a temporary storage block when a writing destination block has already data written. Then, data writing step writing an incoming data to be written into the temporarily storage block, managing step including assigning a pair of the writing destination block and the temporarily storage block an index number which corresponds to the pair, and generating a management table which indicates the index number associating with a physical address indicating a physical position of the temporarily storage block in the nonvolatile memory are performed. In the data writing step, the physical address which corresponds to the index number assigned to the writing destination block is obtained from the management table. The incoming data to be written is written into the temporary storage block indicated by the physical address.