PURPOSE: An automatic opening/closing apparatus of a ventilation window on a greenhouse is provided to enable users to easily install the apparatus into an arch shape identical to a house main body. CONSTITUTION: An automatic opening/closing apparatus of a ventilation window on a greenhouse comprises the following: a ventilation window body(12) installed on the upper side of a plastic greenhouse frame pipe(11); a cover fixing the ventilation window body to the frame pipe; a connection rope(15`) operating an opening/closing window(13) installed inside the ventilation window body; and a fixing plate supporting upper and lower rollers(16, 17). The connection rope is fixed to another connection rope(15) operating an elastic spring(21).
