One object of the invention is to provide a polymerizable monomer compound having a predetermined number of silicon atoms, which can give a polymer having advantageous transparency and high oxygen permeability for use as an ophthalmic device, while exhibiting sufficient resistance to hydrolysis. Another object of the invention is to provide a method for producing such a monomer compound. The present invention provides a silicone compound of the following formula (1): wherein Z is a radically polymerizable moiety； Q is a substituted or unsubstituted, divalent hydrocarbon group having 1 to 20 carbon atoms, and optionally comprising one or more bonds selected from the group consisting of an amide bond, an ether bond, an ester bond and an unsaturated bond； n is an integer of from 1 to 100； and R 1 , R 2 and R 3 are each an unsubstituted, saturated or unsaturated, monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted form of the monovalent hydrocarbon group in which a part or all of the hydrogen atoms bonded to the carbon atoms are each substituted with a functional group or a halogen atom； and wherein the residue R 1 R 2 R 3 Si- has a steric parameter value of -1.00 or less, the parameter indicating the steric bulkiness of the unsubstituted hydrocarbon groups bonded to the silicon atom, and in a case where at least one of R 1 , R 2 and R 3 is a substituted hydrocarbon group, the steric parameter value of the residue in which each of the functional group and halogen atom bonded to the carbon atom of the substituted hydrocarbon group is supposed to be substituted with a hydrogen atom is -1.00 or less. The present invention also provides a method for preparing the silicone compound.
