A window includes a base region and a compressive stress region disposed on the base region. The compressive stress region includes Li+, Na+, and K+ ions. The compressive stress region includes a first compressive stress portion in which a concentration of the K+ ions decreases, a concentration of Na+ ions increases, and a concentration of the Li+ ions increases, from a surface of the window toward the base region. A second compressive stress portion is adjacent to the first compressive stress portion. In the second compressive stress portion, the concentration of the Na+ ion decreases and the concentration of the Li+ ion increases, from the first compressive stress portion toward the base region. The window thereby has a high surface compressive stress value and impact resistance.