A ventilator includes an opening formed on a bottom surface, a rectangular frame provided with a flange, a volute provided with a fan motor inside, and a connector connected to an air outlet of the volute. Four side surfaces of the frame excluding the top surface and the bottom surface tilt towards the outer lower side in a direction from the top surface to the bottom surface, and the opening area of the bottom surface is larger than that of the top surface. The ventilator saves packaging and installation costs, and further facilitates installation between the roof and the ceiling.