A nonvolatile memory device may include a substrate; a first stacked structure on the substrate; a second stacked structure on the first stacked structure; a channel structure including a first portion passing through the first stacked structure and a second portion passing through the second stacked structure; and a filling structure including a first portion passing through the first stacked structure and extending in a first horizontal direction and a second portion passing through the second stacked structure and extending in the first horizontal direction. The upper end of the first portion of the filling structure may be at a same height as the upper end of the first portion of the channel structure.