A flash memory device wherein off cell margin is increased by controlling a voltage of a sensing node and a corresponding reading method, wherein the flash memory device includes a memory cell array; a sensing node voltage controller generating a precharge voltage and a sensing node voltage control signal; and a page buffer unit connected to the memory cell array through bit lines and having page buffers. The page buffers include a bit line connection unit connected between a corresponding bit line and a sensing node, that controls a voltage of the sensing node according to the sensing node voltage control signal; a precharge unit which precharges the sensing node according to the precharge voltage responsive to a precharge control signal; and a data input/output unit sensing a voltage level of the sensing node responsive to a latch control signal and outputting the data of the selected memory cell.