A power adapter includes a shell, a power converter, a first power line, a second power line, a switch received in the shell, and a DC plug. The first power line connects the power rectifier to an external power source, and includes a first terminal and a second terminal. The second power line connects the power rectifier to the DC plug. The switch includes a fixed shaft fixed on the shell, a rotating plate rotatably positioned on the fixed shaft, a number of poles equidistantly disposed on the rotating plate, a number of conductive sheets for conducting the first and second terminal, and a stirring device connecting to the second power line. The conductive sheets are disposed on the rotating plate corresponding to the odd/even poles. When the second power line is pulled, the stirring device rotates the rotating plate to electrically connect or disconnect the first and second terminal.