A nonvolatile semiconductor device includes a first flash memory device; a second flash memory device in which data programming and/or reading is faster than in said first flash memory device; an address conversion table which correlates a logical address of a memory cell to a physical address designating said memory cell of said first and/or said second flash memory; an interface part which accepts an access request to a memory cell, an address conversion table search part which searches a physical address an access part which accesses a memory cell a counting part which counts the number of times a physical address has been accessed and generates an access count value of said physical address; a comparison part which compares whether said access count value of said physical address is more than a threshold or not; and a transmitting part which transmits data to said second flash memory device.