To provide an opening section device equipped with an interlocking mechanism which facilitates locking of both a main lock and an auxiliary lock, and maintains a locking state of the auxiliary lock even if the main lock is unlocked.

The opening section device 1 is formed of the main lock 40, the auxiliary lock 45, and the interlocking mechanism 50 arranged astride the main lock and the auxiliary lock. The opening section device is further formed of a main lock-side interlocking section 60 which is arranged in the interlocking mechanism, and movable or rotatable by following locking operation of the main lock, an auxiliary lock-side interlocking section 65 which is movably or rotatably arranged in the interlocking mechanism, to lock/unlock the auxiliary lock, and an annular wire 51b wrap-connected to the main lock-side interlocking section and the auxiliary lock-side interlocking section. Herein the interlocking mechanism is automatically switchable to an interlocking mode in which the auxiliary lock can be locked via locking operation of the main lock, and to a non-interlocking mode in which the main lock or the auxiliary lock cannot be unlocked even via unlocking operation of the other lock, i.e. the auxiliary lock or the main lock.