PROBLEM TO BE SOLVED: To prevent raindrops to the inside at skylight opening time by suspending a cover suspending to the outside surface side of an opening part from a rotary end part of a roof material for opening-closing/rotating a skylight of a greenhouse so that the lower end is positioned in a free space by separating to the outside surface side of the opening part from an insect proof net. SOLUTION: A cover 5 for guiding rainwater flowing down on a roof material 12 to a rain gutter (b) is suspended to the outer surface side of an opening part (w) from an upper surface of the upper edge 20 of an insect proof net 2 fastened to and installed on an aggregate 120 of a rotary end part of the roof material 12 for forming the upper edge of the opening part (w) in a state of opening the opening part (w), and is also suspended while separating outward from the insect proof net 2 to be installed so that the lower end 50 is positioned in a free space. The cover 5 vertically bends in an outside position of the closed opening part (w) when the opening part (w) is closed. Thus, when there is a rainfall at opening time of the opening part (w), rainwater does not drip in a greenhouse since the rainwater falls on the rain gutter (b) by going along the cover 5.
