One of the purposes of the present invention is to provide a polysiloxane macromonomer which has high hydrophilicity and a narrow molecular weight distribution and is usable as a material for ophthalmic lenses. The present invention provides a both-terminal modified polysiloxane macromonomer represented by the following average structural formula [I′]: R′Me2SiO(Me2SiO)pSiMe2R′  [I′] wherein R′ represents —C3H6O(C2H4O)qC(═O)NH(C2H4O)rC(═O)C(Q)═CH2, Me is a methyl group, p is an integer of from 40 to 100, q is an integer of from 5 to 10, r is an integer of from 2 to 3 and Q is a methyl group or a hydrogen atom. The both-terminal modified polysiloxane macromonomer according to claim 1, having a molecular weight distribution, Mw/Mn, of 1.3 or less.