This experimental study was designed to investigate the effects of Acanthopanax sessiliflorus $S_{EEM}$ leaves, stems, roots (ACL, ACS, ACR) on the change of weight and the serum total cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride, free fatty acid, total lipid and phospholipid level in obese mice induced Dy high fat diet. Experimental groups were as follows ; Normal group was fed with normal diet and administered with distilled water during 7 weeks, Control group was fed with high fat diet and administered with distilled water during 7 weeks, Sample A group was fed with high fat diet and administered with ACL of 500 mg/kg/mouse/day during 7 weeks, Sample B group was fed with high fat diet and administered with ACS of 500 mg/kg/mouse/day during 7 weeks, Sample C group was fed with high fat diet and administered with ACR of 500 mg/kg/mouse/day during 7 weeks. The results were as follows ; 1. Sample A group, Sample B group and Sample C group were significantly decreased the serum total lipid level in comparison with Control group. 2. Sample A group was decreased the body weight (4 weeks, 7 weeks), the serum total cholesterol level, the serum LDL-cholesterol level, the serum triglyceride level, the serum free fatty acid and phospholipid level but increased the serum HDL-cholesterol level in comparison with Control group. 3. Sample B group was increased the serum HDL-cholesterol level but decreased the body weight (4weeks), the serum total cholesterol level, the serum free fatty acid and triglyceride level in comparison with Control group. 4. Sample B group was significantly decreased the body weight (7 weeks), the serum LDL-cholesterol and phospholipid level in comparison with Control group. 5. Sample C group was increased the serum HDL-cholesterol level but decreased the body weight (4 weeks) and the serum free fatty acid level in comparison with Control group. 6. Sample C group was significantly decreased the body weight (7 weeks), the serum total cholesterol level, the serum LDL-cholesterol and triglyceride level in comparison with Control group. According to above results, I suggest ACR is able to be used for the obesity.