Proposed is a flexible cover window manufacturing method capable of simultaneously reinforcing a plane part and a folding part by using alkali-based metal ions having an ionic radius smaller than that of alkali-based metal ions contained in a glass. A flexible cover window manufactured using the same method is also proposed. The plane part and the folding part are simultaneously reinforced using alkali-based metal ions having a smaller ionic radius than alkali-based metal ions included in a glass to simplify the process, and the flexible cover window ensures strength and folding characteristics by controlling tensile stress of the entire part of the flexible cover window.