PROBLEM TO BE SOLVED: To provide a member for preventing flapping motion of a greenhouse sheet with a simple structure, firmly fixing a sheet-winding shaft to a greenhouse and having high operability.SOLUTION: The member for preventing flapping motion of a greenhouse sheet comprises a bottom-opened attaching part to be attached to a ridge-direction member of the greenhouse with a fixing tool and a sheet winding shaft housing part extending from one opened end edge of the attaching part. The sheet winding shaft housing part guides the sheet winding shaft rewound along the outer surface downward in the outdoor direction, and holds the sheet winding shaft on its inner face by the tensioning force of the rewound sheet.
