Since concept testing is highly confidential in an enterprise, little knowledge about desirable design has been shared. The existing literature on factors that improve the quality of concept testing has primarily examined the information extracted from respondents. In other words, while it corresponds to “who” and “what” in concept testing, there is little knowledge about “how.” Therefore, this study investigated an evaluation index that improves the accuracy of sales share estimation in concept testing, targeting the Japanese cosmetics (face wash, latex, lotion) and food (curry, snack, tea) industries. We clarified the relationship between sales performance and the following 10 indices: comprehension, suitability, benefit, realization, reliability, originality, product image, corporate image, attractiveness, and empathy. From the viewpoint of the mean of each index, comprehension is the highest and suitability is the lowest. On the other hand, the correlation with sales share results is the opposite of the above. Suitability, which does not obtain a high score, has the highest correlation with sales performance. With respect to Pearson’s product-moment correlation test, suitability and empathy were observed to demonstrate a significant correlation with sales share at the 5% level. The first element to be formulated in the concept is, “whom is the product for?” If consumers cannot visualize the use of the product themselves, it is difficult to develop a favorable attitude. Accordingly, the fact that the suitability index has a high explanatory power for the sales share matches the framework of the concept.