This study examined the effect of superstars appearing as advertising models on advertising recipients' product evaluations. Specifically, the study tested how product evaluations vary depending on whether the superstar's achievements are relevant to the advertising recipient and how extraordinarily difficult the achievement level is to attain. Additionally, the study examined the mediating process through which the superstar effect occurs. Two experiments were conducted for this purpose. Experiment 1 was designed to examine how the relevance and achievement level of a superstar advertising model affect product evaluations. Participants viewed a print advertisement for a sports car, and the model's relevance (relevant/irrelevant) and achievement level (attainable/unattainable) were experimentally manipulated. The analysis results showed that for irrelevant models, an unattainable achievement level induced relatively more favorable product evaluations than an attainable one, whereas for highly relevant models, the opposite pattern was observed. Experiment 2 was conducted to replicate the results of Experiment 1 and simultaneously examine the mediating process underlying these effects. To this end, items developed to measure several possible mediating processes were added to the experimental design and procedure from Experiment 1. The analysis results, consistent with Experiment 1, revealed a significant interaction effect between the advertising model's relevance and achievement level on product evaluations. Analysis of the mediating process indicated that this effect tended to be mediated by the negative mood experienced by participants while viewing the advertisement. The theoretical and practical implications of these findings are discussed.