There is provided a successive approximation analog-to-digital converter including only minimal capacitors to perform an analog-to-digital conversion operation, thereby making it possible to have very strong process change resistance characteristics while having reduced capacitance and circuit area. The successive approximation analog-to-digital converter may include a reference current supplying unit that supplies a reference current; a signal storage unit that stores a reference signal generated by charging the reference current and an input signal input from the outside; a comparing unit that compares the reference signal and the input signal; and a controller that controls the reference current supplying unit while generating the digital output signal based on the comparison result of the comparing unit to change the supply amount of the reference current supplied to the signal storage unit in proportion to the binary code.