A high resolution digital/analog converting apparatus for a spatial optical modulator includes a resistor string including a plurality of resistors connected to each other in series between operating voltage terminals to divide operating voltages into a plurality of voltages using the plural resistors, a decoder to provide switching signals corresponding to digital signals, and a switch unit to select two voltages from the plural voltages divided by the resistor string according to the switching signal of the decoder. The two voltages are adjacent to each other. Moreover, the digital/analog converting apparatus may include a digital/analog converter to perform a digital/analog conversion of the two voltages.