Provided are a nonvolatile memory device and a method for operating the nonvolatile memory device. The method for operating the nonvolatile memory device includes generating a first program voltage, applying the generated first program voltage to a first word line to which a first memory cell is connected for performing a first program operation on the first memory cell, determining whether a number of pulses of a pumping clock signal for generating the first program voltage is greater than or equal to a predetermined critical value n (where n is a natural number), and stopping the performing of the first program operation on the first memory cell when the number of pulses of the pumping clock signal is determined to be greater than or equal to the predetermined critical value n.