Photooxidation of phenol using singlet oxygen generated in ionic liquid was reported. Singlet oxygen is produced via photosensitized reaction of 5,10,15,20-tetrakis(4-sulfophenyl)porphine in ethylammonium nitrate. The production rate of singlet oxygen was 2.2 times faster than that in aqueous media containing the same. The resulting oxidized product from phenol was pure benzoquinone with no by-product like quinhydrone usually found in aqueous media. The advantage of this method is high yield of benzoquinone with no harmful agents like metal catalysis or oxidizer as well as easy product separation.