A storage device includes a nonvolatile memory device and a controller. The nonvolatile memory device includes a plurality of memory blocks, each of which includes string selection transistors connected to a plurality of string selection lines, ground selection transistors connected to a plurality of ground selection lines, and memory cells connected to a plurality of word lines. The controller reads valid data groups of a first memory block and writes the read valid data groups in a second memory block, during a read reclaim operation. The controller assigns locations of the second memory block, at which the valid data groups are written, based on read counts of the valid data groups.