A cutting tool including a fine and uniform alumina-based substrate is disclosed herein. In an exemplary embodiment, the alumina-based substrate includes 0.1 to 25% by volume of one or more metal oxides, or 5 to 80% by volume of metal carbonitride and 0.01 to 10% by volume of one or more metal oxides. Metal constituting the metal oxide and the metal carbonitride is selected from the group consisting of elements from Groups III to VI (including La group and Ac group) of the periodic table, Mg and Co. The metal oxides added to alumina reside at the boundaries of alumina grains, thereby prohibiting the alumina grains from growing excessively during a sintering process.