We will show that every surjective linear isometry between Hilbert C*-modules over commutative C*-algebras preserves inner products. More precisely, let E and F be two Hilbert C*-modules over commutative C*-algebras A and B, respectively, and T : E → F a surjective linear isometry from E onto F. We will prove that there is a *-isomorphism α: A → B from A onto B such that (The equation is abbreviated)