A nonvolatile memory device with improved reliability is provided. The nonvolatile memory device comprises a substrate, a mold structure including a plurality of word lines stacked on the substrate, a first word line cut region configured to cut the mold structure, a first channel structure spaced apart from the first word line cut region by a first distance, and disposed in the mold structure and the substrate, and a second channel structure spaced apart from the first word line cut region by a second distance, and disposed in the mold structure and the substrate, wherein the second distance is greater than the first distance, a first width of the first channel structure is different from a second width of the second channel structure, and a first length of the first channel structure is different from a second length of the second channel structure.