An object of the present invention is to provide a monomer having a polysiloxane structure and capable of providing a polymer having sufficient compatibility and hydrolysis resistance, while having high oxygen permeability useful for an ophthalmic device, and a method for producing the monomer. The present invention provides a compound represented by the formula (1) which has a radical-polymerizable group at one terminal, one to three alkylsiloxy groups having a hydrophilic and bulky group represented by formula (3-A) or formula (3-B), and has a divalent hydrocarbon group L which has 2 to 20 carbon atoms and may contain one or more selected from an ether bond and a urethane bond, a part of the hydrogen atoms bonded to the carbon atoms may be substituted with a hydroxyl group.
