There is provided a method of producing organopolysiloxanes by using organoalkoxysilanes and/or organoalkoxysiloxanes as starting materials and subjecting them to a hydrolytic condensation reaction, wherein at least 50% by weight of said starting materials is constituted of organoalkoxysilanes and/or organoalkoxysiloxanes represented by an average compositional formula (A):R.sup.1 .sub.a SiX .sub.b Y .sub.c O .sub.(4-a-b-c)/2 (A)wherein R.sup.1 groups are the same or different and each of them represents an unsubstituted or substituted alkyl, alkenyl or aryl group, X represents an alkoxy group containing 1 to 10 carbon atoms, Y represents an alkoxy group containing 2 to 10 carbon atoms which is different from the alkoxy group represented by X and has a hydrolysis rate lower than that of X, a is a real number from 0 to 2, b and c are each a real number from 0.1 to 3, provided that a+b+c.ltoreq.4.