A storage system uses a plurality of flash memory modules and a storage controller. Each of the plurality of flash memory modules comprises a memory controller and at least one flash memory chip. The memory controller manages a plurality of blocks provided with the at least one flash memory chip and controls a first wear-leveling process for leveling erase counts between the plurality of blocks. The storage controller, coupled to the plurality of flash memory modules, controls data sent from a host computer to be sent to a flash memory module of the plurality of flash memory modules. The storage controller controls a second wear-leveling process exchanging data between at least one block of a first flash memory module of the plurality of flash memory modules and at least one block of a second flash memory module of the plurality of flash memory modules.