A nonvolatile memory device includes a memory cell array, a page buffer unit which output a verify-read result, a reference current generating unit which generates a reference current signal, a page buffer decoding unit which outputs currents according to the verify-read result. The nonvolatile memory device further includes an analog bit counting unit which counts the currents, a digital adding unit which calculates an accumulated sum of the counting result, a pass/fail checking unit which outputs a pass signal or fail signal according to the calculation result, and a control unit controlling a program operation.