The present invention provides a polyfluorene oxide having a polymerizable group at both terminals and having a hydrophilic side chain having three or four hydroxyl groups, the polyfluorene oxide being non-colored and transparent. Excellent compatibility with other monomers, especially hydrophilic monomers. A polyfluorene oxide which is represented by the following formula (1): In the formula (1), R 1 is a group represented by the following formula (2), and R 2 is independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and R 3 is independently of each other. The alkyl group having 1 to 6 carbon atoms, A 1 is a group represented by the following formula (3), a is an integer of 1 to 500, and b is an integer of 1 to 100, wherein a + b is 50 to 600] (In the formula (2), n is an integer of 2 to 8, and R 4 is a methyl group or a hydrogen atom) (In the formula (3), m is an integer of 2 to 10, and X is a branchable alkyl group having three or four hydroxyl groups represented by -C p H 2p+1-q (OH) q , p is 1 An integer of ～6, q is 3 or 4).本發明提供一種聚矽氧及其製造方法，所述聚矽氧於兩末端具有聚合性基且具有含三個或四個羥基的親水性側鏈，所述聚矽氧無著色且為透明，與其他單體、尤其是親水性單體的相容性優異。一種聚矽氧，其是由下述式（1）所表示：[式（1）中，R1為下述式（2）所表示的基，R2彼此獨立地為碳數1～10的經取代或未經取代的一價烴基，R3彼此獨立地為碳數1～6的烷基，A1為下述式（3）所表示的基，a為1～500的整數，b為1～100的整數，其中a+b為50～600]（式（2）中，n為2～8的整數，R4為甲基或氫原子）（式（3）中，m為2～10的整數，X為-CpH2p+1-q(OH)q所表示的具有三個或四個羥基的可分支的烷基，p為1～6的整數，q為3或4）。
