A flash memory of the invention has a plurality of planes, a controller, a switch unit, and a driving control circuit. The controller is configured to select at least one of the planes. The switch unit is configured to electrically connect bit lines of the unselected plane to a reference voltage. The driving control circuit is configured to commonly provide a gate select signal to select transistors of the selected planes and the unselected planes after the bit lines of the unselected plane is electrically connected to the reference voltage. A flash memory that can reliably seek stability of threshold distribution of memory is provided.