A manufacturing method of a window includes providing a window including a first non-folding portion, a second non-folding portion, and a folding portion disposed between the first and second non-folding portions and irradiating a laser beam to a front surface of the folding portion of the window to form a first groove in the front surface of the folding portion. The first and second non-folding portions and the folding portion are arranged in the window in a first direction, first processing areas extending in a second direction intersecting the first direction and arranged in the first direction are defined in the front surface of the folding portion, and the laser beam is irradiated at least once to each of the first processing areas in the second direction.