The invention provides an extrusion material supply device suitable for use in melt extrusion molding, and a method for manufacturing an optical transmission body, in which a deterioration of an optical signal transmission loss is extremely small, and productivity intrinsic to an extrusion molding method is provided in combination. An extrusion material supply device 1 includes: a vertical hopper 2, which has a cooling unit 3 and a heat melting unit 4 continuous with a lower portion thereof, and houses a material rod R; cooling means 5 for cooling the cooling unit 3; an electric heater 6 that heats the heat melting unit 4; and gas pressurizing means 7 for sequentially supplying molten plastics M to a metal die by a gas pressure. The heat melting unit 4 is formed into a cylinder shape in which an inner diameter is larger than an inner diameter of the cooling unit 3 arranged above, and enables the molten plastics M to spread in the heat melting unit 4. A portion between an outer circumference of the material rod R and an outer circumference of the molten plastics M is defined as an annular gas pressurizing surface 7a.