A hand-held electronic device having a rolled-up screen comprises a flexible screen which can be partially received within a casing by a reeling mechanism in such a manner that the displaying function can still be performed by the flexible screen partially exposed outside the casing. When the flexible screen is pulled out and entirely exposed outside of the casing, the entire flexible screen can be used for image-displaying. Thus, advantages in both the high displaying quality of a large screen and excellent portability of a small-sized hand-held electronic device can be attained.