A heat-resistant pipe is arranged so as to traverse below a glass ribbon in a float bath of molten tin, and bubbles emanate from the heat-resistant pipe, thereby making the bottom surface (which is in contact with the tin) uneven. Alternatively, the bottom surface is made uneven with a roller for lifting the glass ribbon out of the float bath into an annealing furnace. In addition to these operations for making the glass surface uneven, a film can be applied to the top face of the glass ribbon (i.e. the surface that is not in contact with the tin) by CVD, supplying a mixed gas of raw material from coaters. Thus, the invention makes it possible to manufacture a glass sheet having an uneven surface efficiently, using a technique for processing the surface of a glass sheet that is suitable for a production line for float glass.