A method is provided for verifying a programming operation of a flash memory device. The flash memory device includes at least one memory string in which a string selection transistor, multiple memory cells and a ground selection transistor are connected in series, and the programming operation is performed with respect to a selected memory cell in the memory string. The method includes applying a voltage, obtained by adding a threshold voltage of the string selection transistor to a power supply voltage, to a string selection line connected to the string selection transistor; applying a ground voltage to wordlines connected to each of the memory cells and a ground selection line connected to the ground selection transistor; precharging a bitline connected to the memory string to the power supply voltage; and determining whether a programming operation of the selected memory cell is complete.