A combiner box includes a combiner module and an electrical connector unit disposed in a casing. The combiner module includes an insulating board, and plural first and second input electrodes disposed on opposite surfaces of the insulating board along a first direction and corresponding respectively to plural first and second input sockets of the casing. The second input sockets are disposed below and alternatingly arranged with the first input sockets along the first direction. The electrical connector unit includes plural first and second input terminals disposed in the first and second input sockets and electrically connected to the first and second input electrodes, respectively.