VENTILATOR FOR GREENHOUSE

A ventilator for a plastic greenhouse is provided to evenly ventilate the plastic greenhouse, to control the amount of air entered as well as inner temperature and humidity and to discharge raindrops or snow from the plastic greenhouse. A ventilator is installed in the center of a plastic greenhouse(100) in a longitudinal direction. The ventilator includes a fixed shield, a moving shield and a transferring unit(34). The fixed shield has a plurality of first ventilating holes at constant intervals. The moving shield is located on the top or bottom of the fixed shield to be moved in the longitudinal direction. The moving shield has a plurality of second ventilating holes corresponding to the first ventilating holes. The transferring unit adjusts the overlapping location of the first and second ventilating holes and moves the moving shield to open or close the first ventilating holes. The insect screen is laminated between the fixed shield and the moving shield.