a hollow cylindrical member 626b and a columnar member 126b protruded upward or downward from both upper and lower ends of the cylindrical member 626b and around which the cylindrical member 626b is rotated the protuberance 133 is provided at the upper end of the upper columnar member 126b for controlling the rotation position of the swing wing 626 when the localized flow in the refrigerating compartment 3 is required it is more desirable that a couple of swing wings 626 are installed at the first duct 35a and second duct 36a respectively further a helix wing member 647 is formed on the interior wall of the cylindrical member 626b one side edge 647a of the helix member 647 extends along the interior wall of the cylindrical member 626b another side edge 647b of the helix member 647 slants is offset radially inwardly from the wall toward the center of the cylindrical member 626b on the wall of the cylindrical member 626b there are a plurality of vertically spaced openings 66a 66b 66c the position of respective openings 66a 66b 66c corresponds to the partitioned space between the shelves 8 of the refrigerating compartment 3 at the same traverse point of the slant of the helix member 647 the one side end edge 647a of the helix member 647 is horizontally formed while the other side end edge 647b thereof is slanted upwardly the slant upward angle of the inner edge 647b relative to the outer edge 647a is lowest.