PURPOSE: To improve the haze ratio remarkably, by bringing a flame at a specific temperature or above into contact with the surface of a glass plate heated to a high temperature for a given time or longer, and forming a tin oxide film on the glass plate.

CONSTITUTION: A glass plate 2 is passed through a heating furnace 1 by a conveyor 3, heated and then transferred to a film forming part 10. In the process, the surface of the glass plate 2 is brought into contact with a flame at 420°C or above of a gas burner 7 provided at the outlet of the heating furnace 1 for 0.5sec or longer, preferably 1W5sec. A mixed gas of (CH3)SnCl2 vapor with air is blown from blowing nozzles 4 on the glass plate 2 treated with the flame to form a tin oxide film on the glass plate 2. The glass plate 2 is then sent to an annealing furnace 6 and annealed.