A power source connecting device includes an adapter, a rail and a plurality of power cables. The adapter connected to an external power source converts the alternating current output from the external power source to direct current. The rail electrically connects to the adapter. One end of each of the power cable connected to an electronic device, and another end of each of the power cable connects to the rail and is configured for slide along the rail together with the electronic device. The power cable remains in electrical connection with the rail during the sliding.