An aluminum electrolytic capacitor includes a main body, two electric leads, and a metal set plate. The main body has a base and a plastic insulating film. The electric leads are located at one end of the base. The metal set plate is located at opposite end, with a connecting portion and a soldering portion. The connecting portion is located at the surface of the other end of the base opposite of the two electric leads. The soldering portion extends outside of the main body. The plastic insulating film wraps around the main body and the outer edge of the connecting portion. Thereby, the metal set plate is secured firmly with the main body. The soldering portion of the metal set plate is soldered onto the printed circuit board, allowing the aluminum electrolytic capacitor to be firmly attached to the printed circuit board.