Disclosed is a nano-sized Cu based catalyst and a method of preparing the same including dissolving, in an aqueous solution, a first component comprising a Cu precursor, a second component precursor comprising one or more selected from the group consisting of a transition metal, an alkaline earth metal and a Group IIIb metal, and a third component precursor comprising one or more selected from the group consisting of alumina, silica, silica-alumina, magnesia, titania, zirconia and carbon and then performing stirring; precipitating the stirred mixture solution using Na2CO3 and NaOH to form a catalyst precursor precipitate; and washing and filtering the formed catalyst precursor precipitate. Also a method of preparing alcohol is provided, including reacting hydrogen with carboxylic acid including a single acid or an acid mixture of two or more acids derived from a microorganism fermented solution, using the nano-sized Cu based catalyst.