An apparatus for manufacturing a float glass includes a float bath in which a molten glass moves on a surface of a floatable molten metal to form a glass ribbon, a casing deformation preventing member for allowing an inert gas to flow around an end casing at an outlet of the float bath to prevent the end casing from deforming, a dross box disposed adjacent to a downstream end of the float bath and having lift-out rollers for drawing the glass ribbon, an introduction member for introducing an inert gas into the dross box, and a recycling path for supplying an inert gas, which discharges from the casing deformation preventing member, to the introducing member.