We examined the anti-arteriosclerosis effects of spa treatment in diabetes. We also conducted a comparative study which included non-diabetes patients and diabetes patients who did not receive spa treatment. Methods: Subjects were 104 spa-treated diabetes inpatients at this hospital (Group 1), 60 spa-treated non-diabetes inpatients at this hospital (Group 2), and 28 diabetes patients at other facilities who did not receive spa treatment (Group 3). Ankle-brachial index (ABI) tests were conducted upon admittance and discharge. Results: ABI for diabetes patients (Group 1) showed significant improvement from 1.10±0.01 to 1.12±0.01 on the right side (p<0.01). The left side also showed significant improvement from 1.06±0.02 to 1.09±0.01 (p<0.01). However, non-diabetes patients (Group 2) showed no change on the right side (1.09±0.01 to 1.07±0.02) or left side (1.08±0.01 to 1.06±0.02). Diabetes patients who did not receive spa treatment (Group 3) also showed no change on the right side (1.07±0.03 to 1.05±0.03) or the left side (1.05±0.03 to 1.06±0.03). Discussion: We measured the patients in Group 1, before and after spa treatment, for arteriosclerosis markers Total PAI-1 and high sensitivity C-reactive protein, oxidative stress marker TNF-α, and good adipocytokine adiponectin. Total PAI-1 showed a decrease, and high sensitivity C-reactive protein and TNF-α showed a significant decrease, while adiponectin showed a significant increase. Spa treatment was shown to effectively fight arteriosclerosis and inflammation, and to improve endothelial functions. Conclusion: The changes shown in this study were not seen in non-diabetes patients and diabetes patients who did not receive spa treatment. Therefore, we believe that spa treatment is beneficial for pathological changes caused by diabetes that are particularly skewed towards arteriosclerosis.