The present invention relates to a fibroblast activator comprising grape sap as an active ingredient, a method of activating a fibroblast, using grape sap, and a method of using grape sap as a fibroblast activator. The present invention further relates to a collagen synthesis promoter comprising grape sap as an active ingredient, a method of promoting collagen synthesis using grape sap, and a method of using grape sap as a collagen synthesis promoter. The present invention further relates to a skin antiaging agent comprising grape sap as an active ingredient, a method of preventing aging of skin using grape sap, and a method of using grape sap as a skin antiaging agent. The present invention provides highly safe and effective means of preventing aging.