A model of the appearance evaluation of fresh fish conducted by auctioneers was designed to improve quality control in the distribution of marine products. Three kinds of fish with low body-surface chroma (mean C*ab ≤ 7.0) were graded into five classes by experienced auctioneers. Analysis of appearance evaluations by auctioneers, combined with information on fish coloration and meat freshness, indicated that the color over the central from the thorax in the body best reflected the appearance evaluation and the degree of freshness of the meat. Statistical models were then constructed using four color indexes set on the surface of fish bodies as explanatory variables and evaluated. The results obtained corresponded with the inspections of fish appearance by auctioneers with a certainty of more than 70%. These results confirm the validity of the proposed method, which incorporates the knowledge of auctioneers in the design of a robust marine-product quality evaluation system.