1. An operating method of a memory controller which controls an operation of a non-volatile memory device, the non-volatile memory device including a plurality of memory cells arranged in a direction perpendicular to a substrate, the operating method comprising: erasing the plurality of memory cells; reading memory cells connected with a first word line using a first word line voltage to search string address information corresponding to memory cells being at an off state; and programming memory cells corresponding to the string address information to a particular program state based on the string address information to store mapping information.