A method of operating a non-volatile memory device includes performing a first sensing operation on the non-volatile memory device during a first sensing time including a first section, a second section, and a third section. The performing of the first sensing operation includes applying a first voltage level, which is variable according to a first target voltage level, to a selected word line in the first section, applying a second voltage level, which is different from the first voltage level, to the selected word line in the second section, and applying the first target voltage level, which is different from the second voltage level, to the selected word line in the third section. The first voltage level becomes greater as the first target voltage level becomes greater.