A non-volatile memory device includes a substrate; a memory cell array on the substrate; a control logic circuit configured to output an erase enable signal for controlling an erase operation with respect to the memory cell array; a substrate bias circuit configured to, in response to the erase enable signal, output a first target voltage to the substrate as a substrate bias voltage during a first delay time and, after the first delay time, output the substrate bias voltage to the substrate while gradually increasing a level of the substrate bias voltage to that of an erase voltage having a higher level than the first target voltage; and a row decoder configured to apply a ground voltage to the ground select line based on control of the control logic circuit during the first delay time.