A power supply is provided. The power supply includes a case, an electrical connector and a LED. The case includes a first side wall including an extension part. The extension part is extended from the first side wall toward a second side wall and has an aperture. Portion of the electrical connector is disposed in an accommodation space through an opening and includes a first base and a contacting ring. The first base is disposed in the accommodation space. The contacting ring is disposed on an exterior of the accommodation space. The LED is disposed in the aperture and includes a second base and a lens disposed on the second base. The second base and the contacting ring are located on different surfaces. The lens and portion of the second base are exposed from the opening. The other portion of the second base is covered by the contacting ring.