The present invention relates to a roof ventilation structure for a greenhouse comprising: one side roof portion installed to be inclined upward on one side of an upper portion of a wall body structure of the greenhouse, and where an upper gutter frame is connectedly installed to protrude in parallel in an upper end part the other side roof portion installed to be inclined upward in order to face the one side roof portion on the other side of the upper portion of the wall body structure an opening and closing ceiling portion having a ceiling member vertically installed between a lower portion of the upper gutter frame and an upper portion of the other side roof portion, and made to ventilate by opening and closing a gap between one side roof portion and the other side roof portion as the upper portion is rotationally installed for a certain angle toward the other side with a hinge member as a shaft since a lower end portion of the ceiling member is connected to the other side roof portion through the hinge member and a ventilation control portion. The ventilation control portion has ventilation fan installation frames which are fixedly installed in parallel in a lower portion of a part where roof frames of one side roof portion and the other side roof portion are connected. A plurality of ventilation fans are connectedly installed to be rotatable through the hinge member in the ventilation fan installation frames. Rotating shaft, rotated by driving motors of the rotating shafts, are installed in parallel in a lower portion of one side of the roof frames. A plurality of winding drums are installed in the rotating shafts. A plurality of pulleys are installed at regular intervals on the other side of the roof frames located in upper portions of the ventilation fans. A connecting element wound to each winding drum is connected to the ventilation fans through the pulleys, and rotates the ventilation fans in accordance with a rotation and a reverse rotation of the rotatin
