An output voltage regulating circuit includes a PWM IC, a voltage regulating speed control unit, a first n-type switch unit, a first capacitor, a resistor unit, and a voltage output unit, wherein the voltage regulating speed control unit includes a second switch unit, a second capacitor, a current source, and a comparator; when the PWM IC receives a signal to increase or decrease the output voltage, the PWM IC correspondingly controls the voltage output unit to increase or decrease the output voltage, and simultaneously controls the second switch unit to turn on and then cut off such that the voltage at the first terminal of the second capacitor is gradually increased, and before increasing to the reference voltage, the comparator outputs a high voltage level to turn on the first n-type switch unit such that the compensation terminal of the PWM IC is directly connected to the first capacitor.