A nonvolatile memory device is provided which includes a page buffer unit. The page buffer unit includes a first page buffer including a first A latch configured to store first upper bit data and a first B latch configured to store first lower bit data, and a second page buffer including a second A latch configured to store second upper bit data and a second B latch configured to store second lower bit data. A set pulse may be applied to both the first A latch and the second B latch, or to both the second A latch and the first B latch. The non-volatile memory device may provide high write performance and may respond within a time out period of a handheld terminal.