Quadratic stability analysis is one of the most effective technique to robust stability analysis for systems with parametric uncertainties. In ordinary quadratic stability analysis, quadratic stability of the system which consists of given system matrices (A-matrix), structure of parametric uncertainties, and a region of parametric uncertainties becomes a subject of discussion. In this paper, we evaluate the region of the parametric uncertainties for given system matrices and structure of parametric uncertainties, in which the system is quadratically stable. Though the evaluation is based on scaled H^∞ norm condition which is usually applied to quadratic stability analysis for parametric uncertain system, the evaluation dose not include scaling matrix.