Embodiments include a comparing device having hysteresis characteristics and a voltage regulator using the same. The voltage regulator includes a comparator which compares a comparison voltage with a reference voltage and outputs a result of the comparison, a switching controller which generates a plurality of switching signals in response to the comparison result, resistors connected in the form of a string to divide the comparison voltage into a plurality of voltages, and a switching box which selects one of the plural voltages as the comparison voltage in response to the switching signals.