A non-volatile semiconductor memory device and a driving method for word lines thereof are provided. A flash memory of the invention includes a memory cell array including blocks and a block selection element selecting the block of the memory cell array based on row address information and including a block selection transistor, a level shifter, a boost circuit and a voltage supplying element. The block selection transistor is connected to each word line of the block. The level shifter supplies a voltage to a node connected to a gate of the block selection transistor. The boost circuit boosts a potential of the node. The voltage supplying element supplies an operation voltage to one of the terminals of the block selection transistor. The node, after performing first boosting by the operating voltage supplied by the supplying element, performs second boosting by the second circuit.