We investigated the effect of Protaetia brevitarsis seulensis larvae fermented by Bacillus subtilis (FPb) on the orotic-acid-induced fatty livers of Sprague-Dawley (SD) rats. FPb was found to reduce SD-rat organ size and serum triglyceride levels. Conversely, serum lipid levels were elevated to normal levels, which helped to improve the liver. Total lipid and free fatty acid levels in the serum were lower in the group fed with FPb than in the group fed with Protaetia brevitarsis seulensis larvae (NPb) and showed an overall improvement in lipid metabolism. In a similar manner, the FPb group exhibited an HDL-cholesterol content that was similar to the normal group fed with NPb compared to the group fed only with orotic acid. On the other hand, the group administered with a high concentration of FPb exhibited intracellular toxicity. Pathological observations of liver tissue also revealed that hepatic lobular liver cells were uniformly arranged in the group fed with FPb powder, thereby improving the fatty liver. Protaetia brevitarsis seulensis larvae fermented by Bacillus subtilis improves the non-alcoholic fatty liver and can be used as an effective health food material for enhancing liver function.