The thesis of theory underdetermination is founded on empirical equivalence. And, empirical equivalence is founded on semantical viewpoint. In my argument, we see that Laudan and Leplin points out this kind of thesis of theory underdetermination is untenable. Their argument is successful at least in part. Semantical viewpoint restricts empirical contents within those derived from a theory, say, empirical consequences, but the position of two people is that such viewpoints cannot defend the thesis of theory underdetermination. However, though Carnap and Popper etc., in Laudan and Leplin’s argument, are closed in empirical equivalence, they do not commit theory underdetermination. Even if we approach problems of philosophy of science in semantical, syntactic viewpoints, we do not necessarily arrive at the thesis of theory underdetermination. It is the case that arguing the relation between theory and evidence in the semantical viewpoints has defects pointed out by Laudan and Leplin. But, two people could not argue that semantical approach has no use in philosophy of science.