Purpose: FGF4 (fibroblast growth factor 4) is a newly characterized gene which was found to be a transforming gene in several cancerous cells. FGF4 expression and amplification has been subsequently observed in several human cancers including stomach cancer, breast cancer, head and neck squamous cell carcinoma, lung cancer and bladder cancer. This study was designed to measure the protein expression of FGF4 in malignant skin cancers. Methods: We examined 8 normal skin tissues and 24 malignant skin tumor tissues which were 8 malignant melanomas, 8 squamous cell carcinomas and 8 basal cell carcinomas. The specimens were analyzed for the protein expression of FGF4 using immunohistochemical staining. To evaluate the amount of expression of FGF4, the histochemical score (HSCORE) was used. Results: FGF4 was expressed more intensely in malignant melanoma, followed by SCC and BCC in immunohistochemistry. The average HSCORE was 0.01 for normal skin, 2.02 for malignant melanoma, 1.28 for squamous cell carcinoma, and 0.27 for basal cell carcinoma, respectively. The expression of FGF4 in malignant melanoma and squamous cell carcinoma was increased in comparison with normal tissues and basal cell cancer, and the difference was statistically significant (p<0.05). The difference between malignant melanoma and squamous cell carcinoma was not statistically significant. Conclusion: These findings provide evidences that the expression of FGF4 plays an important role in malignant melanoma and squamous cell carcinoma progressions. This article demonstrates expression of FGF4 in human skin malignant tumors, and suggests that FGF4 is more expressed in highly aggressive skin tumors.