The memory controller writes and reads data in and from a nonvolatile memory. The nonvolatile memory has a plurality of memory cell blocks, each memory cell block includes a plurality of multi-level cells each capable of storing m-bit data (m is a natural number of two or more), a first page to a m-th page are allocated to the respective m bits of the multi-level cell, the memory controller sequentially writes the data to the memory cells from the first page in ascending order, and comprises a backup unit, and when a write command is received from the outside of the memory controller, in a case where a data write destination of the data in the nonvolatile memory is a n-th (n is a natural number of two to m) page of the multi-level cell, and data is already written in the first to (n-1)th pages, the backup unit copies the already written data to a nonvolatile storable backup region.