The invention relates to a use of mandelic acid for anti-oxidation by applying 0.01 wt.%~30 wt.% of the mandelic acid to skin for scavenging DPPH free radicals and superoxide anion free radicals, wherein the pH value of the mandelic acid is more than or equal to 3.5. Accordingly, the mandelic acid can be further utilized in manufacturing cosmetic compositions for anti-oxidation, so as to slow down skin aging.
