PURPOSE: A torch for synthesizing fine glass particles, improving deposition efficiency of the glass fine particles, enabling high-speed production of parent material of optical fiber, capable of reducing its preparation cost, setting several gas jetting holes having a small diameter inside a raw material extruding hole of the synthetic torch.

CONSTITUTION: The gas jetting holes 25 having a small diameters is set inside the glass raw material extruding hole 21. The titled synthetic torch consists of the inert gas spraying hole 22, the combustible gas and combustion aiding gas spraying holes 23 and 24 besides them. In the synthetic torch 31 shown in the example, the very small eddies 35 and the porous parent material 36 produced by the gas jetting hole 32 with a small diameter, the flame flow 33, fine glass particles 34, and a gas jetted from a hole having a small diameter are exhibited. The prepared porous parent material 36 has improved deposition efficiency of the glass fine particles by 70W80%. In the example, an Ar gas is fed to the nozzle having a small diameter, and other gases are expected to have the same effect.