The invention provides a silicone monomer having high purity and suitable for use in the manufacture of ophthalmic devices, and a contact lens produced from the silicone monomer as a polymerizable component. The silicone monomer is represented by the formula (1): wherein Y1 to Y9 each independently stands for an alkyl group having 1 to 4 carbon atoms, n is an integer of 0 to 3, a and b each independently denotes an integer of 0 or 1, and R stands for a hydrogen atom or a methyl group.