A method of producing a glass preform including: forming a porous glass soot configured by an inner deposition soot deposited on a start material and an outer deposition soot deposited outside the inner deposition soot; and sintering, after the forming, the porous glass soot while doping with fluorine to form a glass body including an inner glass portion and an outer glass layer. An amount of the fluorine, with which the inner deposition soot is doped at the sintering, is equal to or more than 0 g/cm3 and less than an amount of the fluorine with which the outer deposition soot is doped.