PURPOSE: To separate anacardic acid useful as a remedy for acne, preventive for dental caries, antioxidant for food and cosmetic, etc., from cashew oil in high yield and purity by carrying out a liquid-liquid extraction of cashew oil with a specific solvent, thereby concentrating anacardic acid.

CONSTITUTION: Cashew oil is subjected to a liquid-liquid extraction with two kinds of solvents forming two separated layers, i.e. a low-polarity solvent (e.g. n-hexane, n-heptane, cyclohexane or benzene) and a polar solvent (e.g. ethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol or 1,5-pentanediol). Anacardic acid of formula (R is 1,4,7-pentadecatrien-15-yl, 4,7-pentadecadien-15-yl, 7-pentadecylen-15-yl or pentadecyl) existing in cashew oil is separated in purified form from the cashew oil and concentrated in the low-polarity solvent layer by this process.