A method of reading data of a multi-level cell (MLC) flash memory device is disclosed. The method includes reading a least significant bit (LSB) and a most significant bit (MSB) of the data programmed to a plurality of memory cells. Reading each of the LSB and MSB includes; reading a MSB flag indicating whether or not the MSB for memory cells in a page of memory cells has been programmed, performing a first read with respect to a plurality of first bit lines, setting a target voltage in view of the read value of the MSB flag, applying the target voltage to a plurality of second bit lines, and performing a second read with respect to the plurality of second bit lines.