A hinge mechanism includes first and second inner guiding members secured on a base seat, and first and second movable members slidable engaged with the first and second inner guiding members and connected with first and second substrate units. During the movement of the movable members to an upright folded state, inboard end edges of the substrate units are moved away from each other to provide a bending space therebetween for a flexible display attached to the substrate units to be bendably received therein.