PURPOSE: An apparatus, having an opening part in the bottom of a pot for holding a molten glass, and capable of flowing down the molten glass from the opening part and inserting an interlayer material through a mandrel into the central part of the thickness of a plate glass.

CONSTITUTION: An apparatus having a pot 21, containing a molten glass 20, and having an opening part 22 for flowing out the molten glass 20 at the bottom thereof and a rising and lowering mandrel 28, having the lower end thereof facing the above-mentioned opening part 22 and a space part 29 for passing an interlayer material 33, e.g. a wire net, therethrough in the interior of the mandrel 28. A slit orifice 23 is provided at the under surface of the above-mentioned opening part 22, and edge holders 25 are capable of holding the side edges of the molten glass 20 flowing down from the above-mentioned opening part 22. A roll 26 for changing the transferring direction of the molten glass 20 is provided under the edge holders 25 to be in contact with the side edges of the molten glass 20. The interlayer material 33 in a position of the central part in the thickness direction of the molten glass 20 in the form of a plate is transferred to an annealing chamber.