Organopolysilmethylene-siloxane of the formula (1): wherein each R1 is, independently of one another, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms other than an alkenyl group, an alkoxy group, a hydroxy group, and a halogen atom; each R2 is, independently of one another, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms other than an alkenyl group, an alkoxy group, a hydroxy group, a halogen atom, and (R1)3SiCH2—, wherein each R3 is, independently of one another, a hydrogen atom and an alkyl group having 1 to 4 carbon atoms; k is an integer of 1 to 100; and n is an integer of 1 to 1000; said organopolysilmethylene-siloxane having, in a molecule, at least two out of alkoxy groups, hydroxy groups, and halogen atoms bonded to one or more silicon atoms.