We report the cytotoxic effect of pulse duration and wavelength of UVB laser radiation from Li(Lu,Y)F4:Ce laser on human skin fibroblasts. When performing the MTT test 24 h after irradiation, an increase in the viability parameter was observed. Flow cytometry showed that 80.8 ± 6.9% of cells have a damaged membrane and only 6.2 ± 2.2% reach the stage of late apoptosis, due to which they have the potential to restore the cytoplasmic membrane and subsequently divide.