A leakage current suppression circuit for an AC-to-DC power supply, the AC-to-DC power supply including an input unit, which includes a first input end (P 1) and a second input end (P 2) cooperatively receiving an AC input voltage, and a grounded third end (P 3), a bridge rectifier which is coupled to the first and second input ends (P 1 and P 2) of the input unit for receiving the AC input voltage therefrom, which converts the AC input voltage into a DC voltage and which outputs the DC voltage through a first output terminal (P 4) and a grounded second output terminal (P 5) thereof, a DC-to-DC converter which is coupled to the first and second output terminals (P 4 and P 5) of the bridge rectifier for receiving the DC voltage from the bridge rectifier, which converts the DC voltage into a predetermined DC output voltage and which outputs the predetermined DC output voltage through a first output end (P 6) and a grounded second output end (P 7) thereof, and a capacitor (C y) which has two terminals, one of which is coupled to the second output terminal (P 5) of the bridge rectifier, the grounded second output terminal (P 5) being connected to a different ground than the ground of the grounded third end and the ground of the grounded second output end, said leakage current suppression circuit characterized by: a first output terminal to be coupled to the third end of the input unit; and a second output terminal to be coupled to the other of the terminals of the capacitor (Cy); and a third output terminal to be coupled to the second output end of the DC-to-DC converter; and a first impedance unit connected electrically between said first output terminal and said second output terminal; and a second impedance unit connected electrically between said second output terminal and said third output terminal; wherein a leakage current (I lk) can flow from the capacitor (C y) of the AC-to-DC power supply into a common node among said first impedance unit, said second impedance unit and the capacitor (C y), and wherein said first impedance unit and said second impedance unit are provided to split the leakage current (I lk) into two current components flowing through said first impedance unit and said second impedance unit, respectively. a first output terminal to be coupled to the third end of the input unit; and a second output terminal to be coupled to the other of the terminals of the capacitor (Cy); and a third output terminal to be coupled to the second output end of the DC-to-DC converter; and a first impedance unit connected electrically between said first output terminal and said second output terminal; and a second impedance unit connected electrically between said second output terminal and said third output terminal; wherein a leakage current (I lk) can flow from the capacitor (C y) of the AC-to-DC power supply into a common node among said first impedance unit, said second impedance unit and the capacitor (C y), and wherein said first impedance unit and said second impedance unit are provided to split the leakage current (I lk) into two current components flowing through said first impedance unit and said second impedance unit, respectively.