This study evaluated the applicability of ‘Baromi2’ (B2) rice flour as a functional ingredient in lean bread by replacing wheat flour at levels of 10%, 20%, and 30%. Bread was produced under standardized baking conditions, and its quality characteristics were assessed through physicochemical analyses (including specific volume, texture, and color). The internal crumb structure was also examined to assess gluten network integrity. As the substitution level increased, finished product volume decreased and crumb hardness significantly increased, indicating weakening of the gluten network. Internal structure analysis revealed that higher substitution levels and reduced pore evenness. Among the samples, the 10% substitution level produced bread with the most balanced texture and crumb structure. These results suggest that ‘B2’ rice flour can be used to partially replace wheat flour in lean bread to enhance nutritional diversity and maintain product quality.