PROBLEM TO BE SOLVED: To provide a speed changing device improving operability by reducing operation force for winding up a greenhouse sheet, while improving operation efficiency in rolling back the greenhouse sheet by enhancing rollback speed and shortening required time, and a greenhouse sheet winder having the speed changing device. SOLUTION: The speed changing device comprises a drive gear 23, a separate follower gear 24 installed in series to the drive gear, a transmission gear, a transmission changeover means 3, a change over operation material 4 for changing the changeover means 3 into a uniform speed transmission and a variable speed transmission and a casing 5 for housing them, and carries out the uniform speed transmission by directly linking a first axis 21 with a second axis 22 through reciprocal operation of the change over operation material 4, while carries out the variable speed transmission by linking the first axis with the second axis by the drive gear 23 using the follower gear 24 as the transmission material. The device for opening and closing the greenhouse sheet having the speed changing device is also provided. COPYRIGHT: (C)2006,JPO&NCIPI
