PURPOSE: To provide the die with high shape and surface precision at the time of high temp. using and to permit the forming of a flats glass having uniform thickness and prolonged service life by raising the temp. of a cladding sheet and a refractory material in the range of a discharging lip part to the one higher than the using temp. in the die while the air between the cladding sheet and the refractory material is vacuum-sucked.

CONSTITUTION: Molten glass 18 discharged from a discharging pipe 17 fitted to the bottom of a glass molten vessel passes through an induction gradient part 15 from a glass inflow part 14 and runs down from a discharging lip part 6. At this time, the molten glass 18 runs while it gradually widens its width because, in the induction gradient part 15, its wide is moderately expanded toward its tip part. Next, the glass 18 overflowing from the tip part of the induction gradient part 15 runs down along the falling gradient face of the discharging lip part 16 while it maintains its width, is formed to be the flat glass and is sent to an annealing furnace. The whole part of the discharging lip part 16 and a part of the induction gradient part 15 do not deform at the time of using and have accurate shape and surface precision for a long period of time. Thus, the thickness of the flat glass to be formed is made uniform, and the service life of the die is extremely prolonged.