A nonvolatile memory device includes a memory cell array, a voltage generator, a page buffer circuit, a row decoder and a control circuit. The memory cell array includes a plurality of mats corresponding to different bit-lines. The voltage generator generates word-line voltages applied to the memory cell array. The page buffer circuit is coupled to the memory cell array through bit-lines. The rowdecoder is coupled to the memory cell array through word-lines, and the row decoder transfers the word-line voltages to the memory cell array. The control circuit controls the voltage generator, the row decoder and the page buffer circuit based on a command and an address. The control circuit selects a voltage between different voltages to apply the selected different voltages to at least one of the word-lines or at least one of the bit-lines according to a number of mats of the plurality mats, which operate simultaneously.