According to one embodiment, a memory system controls a plurality of parallel access units each of which includes a plurality of blocks belonging to the different nonvolatile memory chips. The memory system stores information indicating address conversion rules prescribed such that the number of defective blocks included in the parallel access units is equal to or smaller than a first number. Each of the address conversion rules indicates a mathematical rule for converting a block address to be sent to each of the nonvolatile memory chips into another block address. An address conversion circuit in the memory system converts each of block addresses to be sent to each nonvolatile memory chip into another block address, based on each mathematical rule.