In this study, a new method of measurement and evaluation for optical distortion of glass or transparent objects is proposed. The parameter "CP-contrast" that means the contrast of checkered pattern viewed through the object is selected as evaluating value of the method. In the previous paper, the strong correlation is confirmed between the CP-contrast and the magnitude.of optical distortion determined from surface profile and installation angle. In this paper, relation between the CP-contrast and the human sensitivity is examined. The CP-contrasts and probabilities discriminated by testee are measured for each artificial sample with various installation angles. The sensory scores corresponding to human sensing magnitude of optical distortion are calculated from the probabilities. Strong correlation (r2=0.84) between the CP-contrast and the sensory score is shown, and accuracy of the evaluation by the CP-contrast is higher than that by testee including individual difference and reproducibility. As the next step, dot type optical distortion defects on windshield glasses are evaluated by the CP-contrast and expert inspectors. Strong correlation (r2=0.82) between the both results is observed. It is shown that measuring the CP-contrast can substitute for visual inspection.