A new quantitative evaluation method and the formula for vitreous enamel were proposed. The three-point bending strength was measured by loading on the superposition of test piece which sandwiched glass layer partly between two steel sheets. The adhesion strength (sigma) was calculated using the following equation, sigma = 3PLh/2b.Eg/{Egh(3) + Es(h＇(3) -h(3))}w here, P; bending strength, L; length of span, b; width of glass layer, Eg; Young＇s modulus of glass, Es; Young＇s modulus of steel, h; thickness of glass layer, h＇; thickness of superposition of test piece. The evaluation method for vitreous enamel of this experiment agreed with the empirical evaluation and may be applied to an actual situation.