Spherical silica powder is produced by feeding silica powder having an average particle size of 0.3-40 &mgr;m to a burner flame formed with a flammable gas so as to continuously melt and spheroidize the particles within the flame. The use of a non-halogenated siloxane and/or alkoxysilane as an auxiliary flame-generating source raises the flame temperature and increases the length of the composite flame formed by combustion of the fuel gas with the siloxane or alkoxysilane. Moreover, the fine particles of silica that form as a result of siloxane or alkoxysilane combustion unite and coalesce with the particles of starting silica. These effects accelerate melting and spheroidization of the starting silica powder, resulting in thermally efficient and cost-effective spherical silica powder production.