A molten glass supply device provided with a supply pipe which transfers molten glass from a molten glass production area to a float bath, and also with a weir which is liftably provided at the opening section at the downstream end of the supply pipe and which adjusts the amount of supply of the molten glass to the float bath. The weir has a round-shaped region located on the opening section side. If the vertical dimension of the opening section at the center in the widthwise direction thereof is h, the vertical dimension of the round-shaped region is 0.4h or greater.