Objectives : The present study purposed to examine the effect of Cudraniae Lignum, which is the wooden part of Cudrania tricuspidata Bureau (Moraceae), on cytokine secretion from the joint cells of mice with arthritis induced by collagen and verify its efficacy against rheumatoid arthritis. Methods : We prepared the hot-water extract, ethanol extract and methanol extract of Cudraniae Lignum, and tested their effects on cytokine secretion from the joint cells of mice with arthritis induced by collagen. Results : 1. Cudraniae Lignum reduced the secretion of inflammatory cytokines such as IL-1$eta$, INF-$alpha$ and IL-6 from joint cells. 2. The effect for reducing the secretion of IL-1$eta$, TNF-$alpha$ and IL-6 was strong in order of methanol extract, ethanol extract and hot water extract. 3. Considering the effect on cytokine secretion, the effective element is soluble in organic solvent, and is not volatile. 4. The ethanol extract and methanol extract of Cudraniae Lignum lowered the survival rate of cells significantly, but still the survival rate was over 92%, suggesting the low toxicity of the extracts. Conclusions : Cudraniae Lignum is considered effective for rheumatoid arthritis, and the effective element is considered soluble in organic solvent.