A metal oxide catalyst synthesized using supercritical carbon dioxide extraction is provided, wherein the metal oxide catalyst includes an active site containing at least one type of metal oxide and a support for loading the active site and the metal oxide is an oxide of a metal selected from the group consisting of transition metals (atomic number 21 to 29, 39 to 47, 72 to 79, or 104 to 108), lanthanide (atomic number 57 to 71), post-transition metals (atomic number 13, 30 to 31, 48 to 50, 80 to 84, and 112), and metalloids (atomic number 14, 32 to 33, 51 to 52, and 85) in the periodic table, and a combination thereof.