An oil collection tray includes a flange and a tray body which is inclined inward. The tray body has an inner wall which is inclined inward. The tray body has a plurality of spaced vertical recesses formed on an outer wall thereof and a plurality of protruding ribs formed on the inner wall thereof corresponding in position to the vertical recesses. When a number of oil collection trays are piled up, the tray body of the upper oil collection tray is placed into the tray body of the lower oil collection tray. The tray body of the upper oil collection tray extrudes the air O inside the tray body of the lower oil collection tray.