An exemplary power adapter includes a plug member and a housing. The plug member includes a base and a pair of conductive pins located on the base. A number of protrusions protrude from a side of the base. The housing includes a receiving space for receiving the conductive pins. A receiving slot is located on the sidewall of the receiving space. A number of guiding cutouts extends from a top surface of the housing. The guiding cutouts are in communication with the receiving slot and the receiving space.