The purpose of this study was to evaluate the effect of (-)-Epigallocatechin-3-gallate (EGCG) on the viability of human periodontal ligament fibroblast (hPDLF). Firstly, various concentration of EGCG were applied to hPDLF for 8 days, and then 10 μM EGCG was put for the first 6 days to the experimental group and was stopped for the next 8days. For the positive control group, the 10 μM EGCG was supplied during the whole period, while any EGCG was not supplied for the negative control. Cell viability was analyzed with MTT assay. In the first experiment, the group which treated 10 μM EGCG for 6days showed highest cell viability. In the second treatment, the negative control showed continuous growing up in cell proliferation until 12th day and then a little decreased. After stopping EGCG supply, the experimental group’s proliferation was slightly cut down and then showed big increases. Lastly, the positive control°Øs increase was lasted during the whole period, but there was no a large variance and it showed lowest cell viability on 14th day. From these results, we concluded that EGCG do not affect such a lot on the increase of hPDLF proliferation, but it is possible for EGCG to make hPDLF hibernate with proper concentration of EGCG.