A nonvolatile memory device includes a memory cell region including first metal pads and a memory cell array, and a peripheral circuit region including second metal pads, row decoder circuitry that is connected to the rows of the memory cells through word lines and controls voltages of the word lines, and page buffer circuitry that is connected to the columns of the memory cells through bit lines. The page buffer circuitry is configured to obtain first values by performing a first sensing operation on first bit lines of the bit lines through the first transistors and obtain second values by performing a second sensing operation on the second bit lines of the bit lines through the second transistors, wherein the first values or the second values are inverted. The peripheral circuit region is vertically connected to the memory cell region by the metal pads directly.