Color, material, and finish (CMF) are essential to the competitiveness of industrial products. However, in the existing research on CMF from the consumer behavior perspective, there is an insufficient focus on finish, compared with that on color and material. Research on finish is limited to technical methods, and there is a lack of discussion about its impact on consumer purchasing behavior. This study examines the effect of cars' exterior design finish on purchase intention in Japan. The research question is, "does changing the quality of the finish by removing cut lines have a positive effect on purchase intention?" Two sets of images were used: normal images of car exteriors and images of car exteriors improved by removing cut lines. An online survey was conducted to explore the impact of a car's finish on consumers' purchase intentions in the Japanese market. The randomized controlled trial results showed that finish had a significant positive effect on purchase intention. This study analyzes the interaction of finish with consumer characteristics. A multiple regression model with interactions revealed that, among consumers who emphasize design, a higher finish quality prompted a greater positive influence on purchase intention. In design research, styling tends to attract significant attention. However, practitioners should not neglect efforts to improve finishing when manufacturing products. Companies that consider it impossible to convey to consumers the quality of products with delicate finishing need to change their mindset. These suggestions apply not only to the automotive industry but also to other durable consumer goods industries.