A voltage-regulating device for charge pump is disclosed. The charge pump outputs an output voltage according to the operation of at least one clock signal. The voltage-regulating device includes at least one voltage regulating capacitor and at least inverter. The inverter is for receiving the clock signal and outputting an inverse clock signal accordingly. The voltage regulating capacitor has one terminal coupled to the output voltage and the other terminal coupled to the inverter for receiving the inverse clock signal. The width of a PMOS transistor is different from the width of an NMOS transistor in the inverter.