A voltage regulator includes a main driving stage circuit, a first pre-driving circuit, a plurality of auxiliary driving stage circuits, a second pre-driving circuit, and a comparison and decoding circuit. The main driving stage circuit provides a main driving current of an output voltage according to a first control signal. Each of the auxiliary driving stage circuits determines whether to provide an auxiliary driving current of the output voltage according to a second control signal. The second pre-driving circuit generates the second control signal according to an enable signal. The comparison and decoding circuit generates a simulated driving current and generates a load current according to a reference current and a counting code, compares the simulated driving current with the load current to generate a comparison result, and generates the enable signal by decoding the comparison result. The counting code is generated according to the comparison result.