Abstract: Provided herein is a method for upgrading a bio-oil using a supercritical alcohol, and the bio-oil upgraded by the method, the method including removing oxygen existing in the molecule of the bio-oil using the supercritical state alcohol as a solvent and reacting the bio-oil and the alcohol solvent at supercritical state so as to increase the energy content, removing organic acids that increase the acidity of the bio-oil including formic acid and acetic acid or converting the organic acids to other materials so as to reduce the acidity, and converting hydrophilic materials in the bio-oil to hydrophobic materials so as to reduce the moisture content, and increasing the pH of the bio-oil to reduce the corrosiveness, thereby providing the effectiveness in upgrading a bio-oil.