The purpose of this study was to observe the effects of far-infrared on rheumatoid arthritis induced rats by type ⅡI collagen with the change of arthritis index, hind paw volume, TNF-α and histopathologic findings. Thirty-six Sprauge-Dawley rats which were divided into four group. Group Ⅰ : Normal group, Group Ⅱ : Collagen-Induced Arthritis group, Group Ⅲ : Far-Infrared 25㎝ radiation group, Group Ⅳ : Far-Infrared 35㎝ radiation group. The results of this study were as follows: In arthritis index, far-infrared radiation group(Ⅲ, Ⅳ) are more decreased than collagen-induced arthritis group(Ⅱ). Group Ⅲ and Ⅳ showed the most significant effect at 14 day(p<0.05). In hind paw, far-infrared 25㎝ radiation group(Ⅲ) significantly decreased more than only collagen-induced arthritis group on day 14(p<0.05). Far-infrared 35㎝ radiation group(Ⅳ) significantly decreased more than collagen-induced arthritis group on day 3, 7 and 14(p<0.05). In the ELISA study of TNF-α concentration, collagen-induced arthritis group significantly increased in the concentration more than normal group. Far-infrared radiation group(Ⅲ, Ⅳ) decreased in TNF-α concentration more than collagen-induced arthritis group(Ⅱ) on day 14. In histopathologic findings, collagen-induced arthritis(Ⅱ) and far-infrared 25㎝ radiation group(Ⅲ) increased in synovial membrane thickness on 3 day. Far-infrared 35 em radiation group(Ⅳ) decreased in the concentration more than collagen-induced arthritis group on day 14. The above results suggest that far-infrared radiation effectively reduced in rheumatoid arthritis. It would be considered that far-infrared has an effects on relieving rheumatoid arthritis.