A nonvolatile memory device including a plurality of memory cells arranged at a region where a word line and a bit line cross each other, a voltage generator configured to generate a program voltage to apply to the word line by increasing the program voltage by an increment whenever a program loop is repeated, a current sensing check unit configured to compare a number of failed memory cells among the memory cells to first and second reference values, and a control logic configured to control the voltage generator to change the increment according to the comparison result of the current sensing check unit.