In this study, 30 essential oils available in the market were evaluated for inhibitory activity against 5α-reductase. The essential oils of Santalum album, Matricaria recutita, Pogostemon cablin, and Rosa × damascena(absolute) were observed to exhibit inhibitory activities against 5α-reductase. Gas chromatography-mass spectrometry (GC-MS) analysis was performed to identify the main components of each essential oil. The main components detected in Matricaria recutita, Rosa × damascena, and Pogostemon cablin, were bisabolol oxide A, 2-phenyl ethyl alcohol, and patchouli alcohol respectively. Furthermore, evaluation of the inhibitory activity of these compounds demonstrated that patchouli alcohol was the only component to inhibit 5α-reductase (50% inhibition concentration: 29.8 mg/mL (133 µM)).These findings indicate that patchouli alcohol was one of the active components within the essential oil of Pogostemon cablin. The biological activities of essential oils can be attributed to the various components present in the oil. Therefore, not only major compounds but also the minor compounds should be analyzed for the quality control of essential oils.