Twenty eight compounds were isolated from the whole plant of Euphorbia jolkinii and evaluated for inhibitory effect on $5{alpha}-reductase$ activity. Among the tested compounds, 1-desgalloyl eugeniin, hippomanin A, euphorbin D, exocoecarianin, rugosin E, and pentagalloyl glucose showed potent inhibitory effect on the enzyme activity. The inhibitory potency of rugosin E and euphorbin D, which are dimeric ellagitannins on $5{alpha}-reductase$ activity, was 7-to 8-fold stronger than that of ${gamma}-linolenic$ acid.