The operability of a swinging mechanism for swinging slats is improved, and the functions such as circulation, ventilation, and lighting by an opening covering device are enhanced by the winging mechanism. Slats (2) are arranged horizontally in a rain shutter door frame composed of upper and lower stiles (10, 11), left and right stiles (12, 13), and a central stile (14). An operating slider (15) for operating the swinging mechanism faces to the central stile (14). The sliding force of the operating slider (15) is converted to a rotational force by a twisting bar (3) and transmitted to the slats (2) through a first transmitting member (5), a bar member (4), and a second transmitting member (6).