The invention discloses a device for connecting a ship power supply and a shore power supply in parallel. The device comprises a shell and three layers of copper plates arranged inside the shell. Insulation areas and cooling areas are arranged between adjacent copper plates. Each insulation area is equipped with an insulation pad for insulating and supporting the corresponding copper plate. Each cooling area is equipped with cooling fins. A cable socket is arranged on the front of the shell, and a shore power box socket is arranged on the back of the shell. The three layers of copper plates are connected with the cable socket and the shore power box socket. By adopting the technical scheme of the invention, movement and operation are facilitated, and the flexibility and efficiency of ship connection to the shore power supply are improved.