According to one embodiment, a memory system includes: a memory area; a transfer processing unit that stores write data received from a host apparatus in the memory area; a delete notification buffer that accumulates a delete notification; and a delete notification processing unit. The delete notification processing unit collectively reads out a plurality of delete notifications from the delete notification buffer and classifies the read-out delete notifications for each unit area. The delete notification processing unit sequentially executes, for each unit area, processing for collectively invalidating write data related to one or more delete notifications classified in a same unit area and, in executing processing for one unit area in the processing sequentially executed for the each unit area, invalidates all write data stored in the one unit area after copying write data excluding write data to be invalidated stored in the one unit area to another unit area.