Objectives : The aim of this study was to authenticate whether fractionated extract of Rumex japonicus HOUTT. (RJ) has anti-inflammatory effects in mouse macrophage, RAW264.7 cells. Methods : Roots of RJ were extracted by methanol for 48hours. The methanol that gained was filtered and freeze dried. The methanol extract was dissolved in water and dichloromethane (DCM). After that, two layers were separated. Ethyl acetate (EA) added to the water layer and separated again. All the layers were filtered and freeze dried and the extracts were tested. Cytotoxic activity of extracts on RAW 264.7 cells was measured using MTS assay. The nitric oxide (NO) production was measured and proinflammatory cytokines and $PGE_2$ were measured by ELISA kit. The levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), I ${kappa}$-B-${alpha}$ and nuclear NF-${kappa}B$ p65 expression were detected by western blot. Results : Our results indicated that DCM and EA extracts of RJ inhibited the LPS-induced NO, $PGE_2$ production and iNOS, COX-2 expression accompanied by an attenuation of TNF-${alpha}$, IL-$1{eta}$ and IL-6 production in RAW 264.7 cells most effectively. DCM and EA extracts also had suppression effects of LPS-induced NF-${kappa}B$ and MAPKs activation. Conclusions : This results demonstrate that fractionated extract of RJ has anti-inflammatory effects and among the fractioned extract, dichloromethane and ethyl acetate extract have best anti-inflammatory effects.