According to one embodiment, a memory controller includes a mode selection part that selects one of a MLC-mode and a SLC-mode, after a write command is decoded by a command decode part, and a write part that executes a data writing to a storage memory by using one of the MLC-mode and the SLC-mode selected by the mode selection part. The mode selection part is configured to check whether a first data wrote from a host to a buffer memory is a time-continuous data that is wrote continuously during a predetermined period, execute the data writing of a second data from the buffer memory to the storage memory in the MLC-mode, when the first data is the time-continuous data, and execute the data writing of the second data from the buffer memory to the storage memory in the SLC-mode, when the first data is not the time-continuous data.