A plurality of terminal boards (30A, 30B) for electrically interconnecting a plus electrode and a minus electrode of a solar cell module and cables (90) for external connection corresponding to the both electrodes are placed on a base plate (11), and two corresponding terminal boards (30A, 30B) are bridged by a bypass diode (50). The respective terminal boards (30A, 30B) juxtaposed on the top surface of the base plate (11) are collectively supported and fixed by a retaining plate (60). Accordingly, the generation of an undue strain in the bypass diode (50) can be avoided even in the case of fixing the terminal boards (30A, 30B) to the base plate (11) with the terminal boards (30A, 30B) bridged by the bypass diode (50) beforehand.