A sealing device for a well plug includes a mandrel device, a sealing element, a first supporting device provided on a first side of the sealing element and a second supporting device provided on a second side of the sealing element. Each supporting device includes proximal supporting elements provided proximal to the sealing element and distal supporting elements, where first ends of the respective proximal and distal supporting elements are pivotably connected to each other. The second ends of the proximal supporting elements are pivotably connected to a connector of a proximal supporting ring. The sealing device is brought from a run state to a first set state by relative axial movement of the distal supporting rings towards each other and relative axial movement of the proximal supporting rings towards each other.