To provide an opening/closing mechanism for a building, which enables manual or automatic opening of a sliding door, a door, or a surface lattice arranged in an entrance or a window of the building in an emergency such as a fire, produces an alarm sound, emits flashlight, and allows persons in the building to quickly and safely evacuate.

The opening/closing partition mechanism 29 arranged in the entrance, the window, or an opening section 9, is set between an end movable frame 7a thereof and a fixed frame 4 of the opening section 9, and has engaging mechanisms arranged in both of the end movable frame 7a and the fixed frame 4, for closing the opening/closing partition mechanism 29 and engaging the end movable frame 7a with the fixed frame 4. Further the opening/closing partition mechanism 29 has an unlocking device 28, an alarming flash lamp 13, and a switch mechanism which are operable in an emergency such as a fire. The unlocking device 28 unlocks the engagement between both the frames. The alarming flash lamp 13 produces an alarm sound, and flashes flashlight. The switch mechanism sets the alarming flash lamp 13 in an inoperable mode in normal times but sets the same in an operable mode in an emergency. The unlocking device 28, when operated, is set in an emergency automatic mode, and automatically cancels the engagement between the end movable frame 7a and the fixed frame 4.