Disclosed is an operating method of a nonvolatile memory device, which includes programming the first selection transistors of the plurality of cell strings and programming the plurality of memory cells of the plurality of cell strings. The programming the first selection transistors comprises supplying a first voltage to a first bit line connected with a first selection transistor to be programmed and a different second voltage to a second bit line connected to a first selection transistor to be program inhibited; turning on the second selection transistors of the plurality of cell strings, and supplying a first program voltage to a selected first selection line among a plurality of first selection lines connected with the first selection transistors and a third voltage to an unselected first selection line among the plurality of first selection lines.