Foldable display device

A foldable display device, comprising:

• a flexible display panel;
• a support module, comprising:
• an intermediate platform having an intermediate support surface and a pair of guiding round surfaces respectively located on two opposite sides of the intermediate support surface to support the flexible display panel;
• and
• a pair of side platforms, each of the pair of side platforms having a side support surface to support the flexible display panel;
• and
• at least one positioning module, comprising:
• a pair of positioning gears fixed to the intermediate platform;
• and
• a pair of planetary gears respectively fixed to the pair of side platforms on a pair of gear axes parallel to each other and engaged with the pair of positioning gears to move around the pair of positioning gears along a pair of motion paths, respectively, so that the pair of side platforms are switched between a flattened state and a folded state with respect to the intermediate platform to flatten or bend the flexible display panel, wherein the pair of motion paths are located on a geometric plane perpendicular to the pair of gear axes and are a pair of involutes symmetrical to each other.