In the past few years, lifestyle-related diseases have been increasing, and meat intake has been linked to this increase. Therefore, in recent years, there have been attempts to use soybeans as a substitute for meat. Soybeans exhibit antioxidant and antimicrobial effects. Therefore, processing foods using soybeans may preserve food quality because the main factors causing food deterioration are oxidation and microbial growth. To verify the quality-retention effect of soybeans, we conducted a sensory test on hamburgers, the quality of which readily deteriorates over time. We investigated the percentage of soybean meat that would be acceptable in a hamburger and quality retention with the addition of different amounts of soybean meat. We found that hamburgers with soybean meat were accepted by more than half of the participants when the soybean meat content was ≤50%. In terms of changes over time in quality-related factors, the L- and b-values (lightness/brightness and yellowness/blueness, respectively) were higher, avalue (redness/greenness) was lower, and pH was higher in hamburgers that contained soybean meat than in those without added soybean meat. Furthermore, an increase in the bacteria count and peroxide content was suppressed in hamburgers containing soybean meat. The results indicate that hamburgers containing soybean meat are of higher quality than those made with 100% animal meat. The use of soybeans as a meat substitute in hamburgers can help mitigate the rise of lifestyle-related diseases linked to high meat consumption.