According to the traditional chinese herbal Cuscuta japonica Choisy and C. australis R.Be (original plant of Semen Cuscutae in Korea) have been used to cure pimple. In order to prove their bacteriostatic effects against Prvpionibacterium acnes, we performed the micro broth dilution method. The minimal inhibitory concentration (MIC) of C. japonica juice was 27.3 mg/ml, but C. australis juice showed no effect. The MIC of water extracted C. japonica seed and Wontosa and Bupjetosa were 960 μm/ml. The MIC of both water and ethanol extracts of C. australis seed was 240 μg/ml. But ethanol extracts of C. japonica seeds, Wontosa and Bupjetosa had no bacteriostatic activity. We also performed the disk diffusion test, C. japonica juice had prominent effect. Water extracts of C. japonica seed, Wontosa and Bupjetosa showed bacterio-static effect in 10 mg/ml, and C. australis seed in 10 mg/ml. The ethanol extract of C. japonica seed, Wontosa, Bupjetosa, and of C. australis seed showed bacteriostatic effect in 20 mg/ml.