Abstract—The advance of biotechnology has provided various benefits to our lives. There is an increase in the opportunity of cell fusion and cultivation for using optical tweezers. Although optical tweezers is useful technique, cells are damaged by laser irradiation. Therefore, in our study, we estimated the cells damage by Ar laser (514nm) and semiconductor laser at 980nm. As a preliminary stage to our study, we trapped cells using optical tweezers at 980nm laser and Ar laser and showed manipulation data of polymer microspheres and yeast cells. Furthermore we calculated trapping power and trapping efficiency from the results of manipulation data. In the next stage, we focused on activity evaluation method using Dielectrophoresis (DEP) as estimating yeast cells damage. We trapped yeast cells by optical tweezers at 980nm laser and Ar laser and observed the movement of cells while changing the time of irradiation. We set the initial value to voltage of 1V and frequency of 500kHz and applied such parameter settings to the electrode by function generator(KENWOOD, FG-281). This experiment proved that optical tweezers at Ar laser was harmful for yeast cells, while optical tweezers at 980nm laser was harmless for yeast cells.