To find alternative agents for bovine mastitis, the extracts of 30 selected herbal medicine were screened for their antibacterial activity against mastitis pathogens. The extracts of 9 herbal medicine, Terminaliae chebula, Cinnamonum loureirii, Paeonia japonica, Inula britannica, Caesalpinia sappan(C. sappan), Salix babylonica, Alpinia katsumadai, Polygonum aviculare and Coptidis japonica showed strong antibacterial activity. Among of them, C. sappan extract was found to be the most active against all bacteria in this experiment. Methanol extract of C. sappan and brazilin, the main component of C. sappan, had inhibitory activity against a variety of pathogens, however they had less of an inhibitory effect on gram negative bacteria. Minimal inhibitory concentrations of brazilin against gram positive pathogens was lower than that of methanol extract. These results showed that the extract of C. sappan has a potential as a therapeutic agent for bovine mastitis.