Abstract: Connecting terminals (25a to 25d) are accommodated side by side in a terminal box casing (21). Diodes (30a to 30c) are connected electrically between the respective connecting terminals (25a to 25d). The diodes (30a to 30c) are connected in series via the intermediate terminal mounts (28a, 28b). Partition walls (24) for partitioning diode accommodation spaces (23a to 23c) for at least partly accommodating the diodes (30a to 30c) are formed in the terminal box casing (21).