Knowledge of experienced auctioneer regarding the circulation of marine products is an essential skill and is necessary for evaluating product quality and managing aspects such as freshness. In this study, the ability of an auctioneer to quickly evaluate the freshness of fish at fish markets was analyzed. Evaluation characteristics used by an auctioneer were characterized and analyzed using a fuzzy logic model. Sixty-two boxes containing 388 swordtip squid (Loligo edulis) with mantles measuring 200 mm that had been evaluated and assigned to one of five quality categories by an auctioneer were used for the analysis. The relationships between the evaluations of appearance (category), body color, and state of the chromatophores were statistically analyzed. It was found that a total of four indexes strongly reflected evaluations of appearance: chromatophore expression on the head, two different chroma states for two points on the mantle and the difference in the color of the mantle and the head. The fuzzy logic model used these indexes premise variable for the language rule. The results of both simulationes and evaluations demonstrated that the model was robust, with the results predicted by the model corresponding with more than 90% of the quality assignments of the auctioneer.