In order to study on SOD like activity and Electric donor ability of Hedyotis diffusa $W_{ILLD}$, testing antibacterial effect on E. coli O157 which causes infectious inflammatory disease; measunng inhibitory effect on tyrosinase which stimulates melanin formation; and measuring the influence of it to SOD like activity, DPPH and TBARS which are related to ageing and carcinogenesis. The results of these experiments, are as follows. 1. In the antibacterial experiment with the extract of Hedyotis diffusa $W_{ILLD}$ on E. coli O157, there was no change in proliferation from the beginning of culture to two hours after, but proliferation inhibiting effect on E. coli O157 was detected from three hours after the beginning of culture. 2. Tyrosinase inhibitory effect was measured as $0.39{pm}0.026%$. Compared with the control group, the effect was very slight. 3. The SOD like activity of the extract of Hedyotis diffusa $W_{ILLD}$. was measured as 21.33${pm}$ 4.264%. Compared with the extracts of several other herbs, it was much more significant. 4. The DPPH of the extract of Hedyotis diffusa $W_{ILLD}$. was $53.3{pm}0.91%$ when 0.02g was used and $83.5{pm}1.82% $ when 0.05g was used. The result when 0.05g was used was more significant than 0.02g was used. 5. The TBARS of the extract of Hedyotis diffusa $W_{ILLD}$. was measured as 0.724 ${pm}$0.O04MDAppm. Compared with the extracts of several other herbs, the result was more significant. From these results, we found that Hedyotis diffusa $W_{ILLD}$. can be used in therapy of dysentery with bloody stool and fever which is caused by infection with E. coli O157 and that it can be also used effectively as age resister or anticarcinogen.