A method and an apparatus for producing a porous glass preform by using organosiloxane raw material is provided. The apparatus for producing the porous glass preform 12 according to the present embodiment is configured to mix organosiloxane in a liquid state being a raw material with a carrier gas in a vaporizer 6, heat this mixture to be vaporized, supply this vapor to a burner 13 as a gas raw material, and produce a porous glass preform by depositing a glass fine particle produced by combusting the gas raw material on a starting material, herein the apparatus for producing a porous glass preform includes a moisture removing apparatus 8 configured to remove moisture in the carrier gas and supply the vaporizer with the carrier gas.