There is provided an organopolysiloxane which is excellent in extensibility as well as solubility and dispersibility in water and lower alcohols. There is provided an organopolysiloxane with a poly(N-acylalkyleneimine) segment having a repeating unit represented by the following general formula (1): wherein R1 represents a hydrogen atom or an alkyl group, an aralkyl group, or an aryl group each having 1 to 22 carbon atoms, and n is 2 or 3, wherein the segment is bound to each of at least two silicon atoms of an organopolysiloxane segment as a main chain via an alkylene group containing a hetero atom, and wherein the number-average molecular weight of the segment is 800 to 1600, the mass ratio of the organopolysiloxane segment as a main chain and the poly(N-acylalkyleneimine) segment is 65/35 to 82/18, and the weight-average molecular weight of the organopolysiloxane segment as a main chain is 10,000 to 100,000.
