PURPOSE: To provide for reduction of cost by moving ups and downs of slats with a structural simplicity, and reducing a number of components and manhours of fabrication.

CONSTITUTION: Many slats 11 that are vertically guided and moved along guide grooves 47 of vertical frames of an opening 3, with both sides of the slats 11 being engaged in the guide grooves 47, are connected with adjacent slats 11 at their ends for being folded one upon another. At least, one slat 11A of the slats 11 is fitted with a tilt arm 51 at the end of its side. And, a cam device 61 is fitted within the vertical frame, and following the vertical movement of the slats 11, the tilt arm 51 is engaged with the cam device 61, resulting in an opening or closing direction of movement of the slat 11A which is provided with the tilt arm 51 and the simultaneous movements of the other slats 11 that are connected with the slats 11A in the opening or closing direction of the movements in concert. Release of the engagement of the tilt arm 51 and the cam device 61 restores the vertical position of the slats 11.