To increase the number of times data can be written into a flash memory a flash memory is provided with a real data block having multiple data blocks each having multiple data write cells. A memory control device identifies a data block having a reprogrammable write cell out of the data block, successively adding received, new data segments into the reprogrammable write cell of the identified data block to complete addition of the data segments. The block in a state before the addition is kept to a certain period of time and then erased in the unit of block. When the number of write operations in the data block reaches a predetermined number of times, then it selects new data blocks that are necessary for retaining a subsequent predetermined number of operations to rewrite data, and repeats the aforementioned operations for the selected data blocks.