An optical condition determination system includes a simulation execution unit that performs an optical simulation on a surface texture model that models a surface texture of a target object of the appearance inspection, and a defect model that models a defect of the target object, under a plurality of optical conditions to generate a surface texture image and a defect image, an image synthesizing unit that synthesizes the surface texture image and the defect image generated by an optical simulation under the same optical condition to generate a synthetic image, an evaluation value calculating unit that calculates an evaluation value representing easiness of detecting the defect in the synthetic image, a correlation analysis unit that analyzes a correlation between an optical condition and the evaluation value corresponding to the synthetic image, and an optimum condition searching unit that searches for the optical condition suitable for the appearance inspection based on an analysis result of the correlation.