According to one embodiment, the memory system includes a nonvolatile semiconductor memory, a data buffer, a volatile memory for storing a management table uniquely associates the user data with an address of the physical storage region of nonvolatile semiconductor memory, a controller that carries out a force quit process for writing the user data stored in a data buffer, the management table stored in volatile memory into the nonvolatile semiconductor memory, and a storage battery. The controller starts the force quit process prior to the power supply of the internal power supply regulator is switched from an external power supply to the storage battery.