A flash memory device including a memory array, a row decoder and M page buffers is provided, wherein M is a positive integer. The memory array includes a plurality of memory cells and is electrically connected to a plurality of word lines and a plurality of bit lines. The row decoder drives a specific word line among the word lines during an enabling period. The M page buffers divide the enabling period into N sub-periods, wherein N is an integer greater than 2. Furthermore, the ith, (i+N)th, (i+2N)th, . . . , (i+(M−1)*N)th bit lines are driven by the M page buffers during the ith sub-period, so as to program the memory cells electrically connected to the specific word line, wherein i is an integer and 1≦i≦N.