A memory system includes a nonvolatile semiconductor memory and a controller. The memory has a plurality memory blocks each including memory cells capable of holding data. The data in each of the memory blocks is erased simultaneously. The data is written simultaneously in pages in each of the memory blocks. Each of the pages is a set of a plurality of memory cells. The controller transfers write data and a first row address to the memory and issues a change instruction for the transferred first row address and a second row address differing from the first row address. The memory writes the write data into the memory cells corresponding to the first row address when the change instruction has not been issued, and writes the write data into the memory cells corresponding to the second row address when the change instruction has been issued.