Low-power laser irradiation on oral mucosae is supposed to have healing effects caused by accelerating cell growth. However, the mechanism of epithelial cell growth caused by laser irradiation is unknown. The aim of this study is to solve effects of low-power laser irradiation on epithelial cell motility which is an important factor in wound healing. Experimental cells were normal human gingival keratinocytes, cultured in keratinocyte growth medium-2 for 2 days. Low-power laser device was trinpl D^[○!R] (905nm, GaAlAs diode, average 2.4mW, YOSHIDA, Tokyo). The cell motility of gingival keratinocytes in vitro were examined by phase contrast microscopy with CCD camera, and the serials image of the same cell photographed every 10 minutes for 360 minutes were analyzed by image analysis software program. Cdc42/Rac which is a member of the Rho family in gingival keratinocytes was examined by confocal laser scanning microscopy using antibody. Cells in non-irradiation group moved toward their forming filopodia and lamellipodia at average speed of 55μm/hr through examination period. In irradiation group, the speed of cell movement increased after laser irradiation, and reached a peak of 90μm/hrin 30 minutes. Afterwards, the speed reduced and was almost the same as non-irradiation group in 300 minutes later. On the other hand, Cdc42/Rac in non-irradiation group was expressed on a part of lamellipodia region of the cell. In irradiation group, expression of Cdc42/Rac was more than in non-irradiation group. From these results, low-power laser irradiation appeared to accelerate cell motility of gingival keratinocyte. Further, low-power laser may influence signal transduction of Rho family related to cell motility in wound healing.