Automotive outer panels may be distorted during heat treatments for curing of structural adhesives and mastic sealers. Distortion occurs due to residual stress between the adhesive and the panel following the curing process of the adhesive. The research discussed in this paper therefore considered a simulation technique of distortion and measuring method using curvature as the evaluative indicator. Curvature refers to the change of gradient of the curved surface, and the difference in curvature between the standard shape of the panel and the distortion section closely resembles the results of visual evaluations. Test panels were manufactured and measurements of their curvature were conducted. A study of the correlation of measurement results with the results of visual evaluations showed a good match. The curvature in a simulation of distortion in which the adhesive was cured between heating and cooling and the adhesive and panel were held fixed in position only during the cooling process accurately matched the results of measurements of curvature taken in the test panels. These studies showed that the results of simulation of distortion using curvature as an evaluative indicator and the results of visual evaluations correspond, and that it is possible to make quantitative evaluation of distortion at design stage and mass-production process.