Objectives : To evaluate the anti-tumor and synergic effect of Soonkiwhajungtang with doxorubicin. Methods : The inhibitory concentration (IC), $IC_{50}$ and $IC_{90}$ of single use of doxorubicin and Soonkiwhajungtang with their concomitant treatment against MKN-45 (human stomach carcinoma) cell line were observed using MTT (microculture tetrazolium test) assay. In addition, their anti-tumor effects were also observed in xenograft nude mice models against the MKN-45 cell line. Results : Soonkiwhajungtang has only minimal direct anti-tumor effect against MKN-45 cell line but it reduced general depressed signs induced by implantation of the tumor cell lines and increased the total WBC and lymphocyte numbers. Conclusions : It is considered or expected that Soonkiwhajungtang extract reduces the critical toxicity of doxorubicin and has favorable synergic anti-tumor effect when administered concomitantly with doxorubicin.