In a semiconductor storage device, a memory controller divides each of blocks in each of chips into a first page set composed of pages and a second page set composed of pages, divides a logical address space into groups, and divides each group into lines. Block units are created each of which is obtained by assembling a predetermined number of blocks from the blocks in each chip. A predetermined number of block units from the block units are managed as standard block units, and the other block units are managed as spare block units. Each standard block unit is made to correspond to one group. The corresponding group data is stored in the pages in the first page set in each block constituting the standard block unit, and unwritten pages for recording update data for the group data are provided to be included in the second page set.