The present invention provides a flash memory device wherein memory cells in each of the memory cell blocks are divided into a plurality of memory cell groups. In each memory cell group, local bit lines are laid out connected by segmentation transistors. When selecting a memory cell, only a local bit line connected to a memory cell selected by an operation of the segmentation transistor is coupled to a global bit line so that the load to be applied to the bit lines is minimized during the read out operation.