Abstract: An improved method for fabricating an optical fiber preform by the vapor phase axial deposition (VAD) method, comprises forming core and cladding soots at the same time by the use of core and cladding burners. The improvement is that the cladding burner is designed so that at least one of the outlets for a feed material gas, a fuel gas, an auxiliary fuel gas, and an inert gas is composed of a plurality of openings. In this improved method, the temperature distribution from the boundary of the core soot to the periphery of the cladding soot is made smooth, and thus the cladding soot is prevented from cracking.