The present invention provides a tin alloy bath for a float bath, an apparatus for manufacturing a float glass, a method for manufacturing a float glass that can provide a high quality float glass in which defects due to coagulation and falling of a volatile tin component have been suppressed, and a float glass manufactured using those. The above-mentioned tin alloy bath for a float bath is a molten metal bath to be placed in the float bath for supplying molten glass to a liquid surface of the molten metal bath, thereby forming into a glass ribbon, and includes 1 mass % or more of copper with the remainder being unavoidable impurities and tin.