Provided is a method for preparing a siloxane polymer by hydrolysis and condensation reactions of a hydrolyzable silane compound, which has a step of preparing a salt of a silsesquioxane cage compound represented by the following formula (1): (SiO.sub.1.5--O).sub.n.sup.n-X.sup.+.sub.n (1) wherein, X represents NR.sub.4, Rs may be the same or different and each represents a linear or branched C.sub.1-4 alkyl group and n is an integer from 6 to 24 and a step of hydrolyzing and condensing the hydrolyzable silane compound with the salt of a silsesquioxane cage compound.