Abstract: A protective case for foldable mobile devices is described. The folding case comprises a first case and a second case, wherein the folding case further comprises a side cover which rotates by an elastic part as the foldable mobile device is folded or unfolded, and provides a full protection for the entire foldable mobile device including each corner of its hinge part. The folding case according to the present invention covers the hinge part smoothly without any unfavorable space or gap, and it provides the satisfaction with the use and the beauty of the overall appearance as the users would conceive that the two separated case parts and the hinge part operates as if those parts form one united case.