The activation of NF-$kappa$B induced by kojic Acid, an inhibitor of tyrosinase for biosynthesis of melanin in melanocytes, was investigated in human transfectant HaCaT and SCC-13 cells. These two keratinocyte cell lines transfected with pNF-$kappa$B-SEAP-NPT plasmid were used to determine the activation of NF-$kappa$B. Transfectant cells release the secretory alkaline phosphatase (SEAP) as a transcription reporter in response to the NF-$kappa$B activity and contain the neomycin phosphotransferase (NPT) gene for the dominant selective marker of geneticin resistance. NF-$kappa$B activation was measured in the SEAP reporter gene assay using a fluorescence detection method. Kojic Acid showed the inhibition of cellular NF-$kappa$B activity in both human keratinocyte transfectants. It could also downregulate the ultraviolet ray (UVR)-induced activation of NF-$kappa$B expression in transfectant HaCaT cells. Moreover, the inhibitory activity of kojic Acid in transfectant HaCaT cells was found to be more potent than known antioxidants, e.g., vitamin C and N~acetyl-L-cysteine. These results indicate that kojic Acid is a potential inhibitor of NF-$kappa$B activation in human keratinocytes, and suggest the hypothesis that NF-$kappa$B activation may be involved in kojic Acid induced anti-melanogenic effect.