The present invention provides an organopolysiloxane obtained by binding, to at least two silicon atoms of an organopolysiloxane segment constituting a main chain, a poly(N-acylalkyleneimine) segment composed of a repeating unit represented by the following formula (1): wherein R 1 represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms and n is 2 or 3, via an alkylene group containing a hetero atom, wherein the poly(N-acylalkyleneimine) segment has a number-average molecular weight of from 1,600 to 3,500； a mass ratio (a/b) of the organopolysiloxane segment (a) constituting the main chain to the poly(N-acylalkyleneimine) segment (b) (which will hereinafter be called "mass ratio (a/b)", simply) is from 42/58 to 58/42； the organopolysiloxane segment between two poly(N-acylalkyleneimine) segments adjacent to each other has a weight-average molecular weight of from 1,600 to 3,500； and the organopolysiloxane segment constituting the main chain has a weight-average molecular weight of 7,000 to 100,000.本發明提供一種有機聚矽氧烷，其係於構成主鏈之有機聚矽氧烷鏈段之矽原子之至少2個上，經由含有雜原子之伸烷基，鍵結包含下述通式(1)所示之重複單元之聚(N-醯基伸烷基亞胺)鏈段而成者：[化1](式中，R1表示氫原子、碳數1~3之烷基，n表示2或3)；並且，聚(N-醯基伸烷基亞胺)鏈段之數量平均分子量為1,600~3,500，構成主鏈之有機聚矽氧烷鏈段(a)與聚(N-醯基伸烷基亞胺)鏈段(b)之質量比(a/b)(以下亦僅稱為「質量比(a/b)」)為42/58~58/42，鄰接之聚(N-醯基伸烷基亞胺)鏈段間之有機聚矽氧烷鏈段之重量平均分子量為1,600~3,500，且構成主鏈之有機聚矽氧烷鏈段之重量平均分子量為7,000~100,000。
