The purpose of the present invention is to provide a polysiloxane monomer which gives an ophthalmic device with excellent wettability and a method for preparing the same. The present invention provides a compound represented by the following formula (1):




wherein R1 is a hydrogen atom or a methyl group, L1 is a single bond or a divalent hydrocarbon group which has 1 to 6 carbon atoms and may have at least one selected from an ether bond, an ester bond, and a urethane bond, Z is a monovalent organic group which has 1 to 10 carbon atoms and has a quaternary ammonium group or an amphoteric ion group, A is a linear or branched organo(poly)siloxanyl group having 1 to 100 siloxane units, L2 is a linear, branched or cyclic, divalent or trivalent hydrocarbon group which has 2 to 10 carbon atoms and may have an ether bond, and L3 is a divalent or trivalent hydrocarbon group having one carbon atom, provided that and when L3 is trivalent, then L2 is also trivalent, and L3 and L2 together form a ring.