A protective case (100, 100A, 100B) for an electronic device with a stretchable display panel, the protective case (100, 100A, 100B) comprising: a backplate (110, 110A, 110B), comprising an accommodating space, wherein the accommodating space is adapted to accommodate the electronic device; a first housing (120, 120A, 120B), comprising a first planar part and slidably disposed on the backplate (110, 110A, 110B), wherein the first housing (120, 120A, 120B) is adapted to abut against a first side of the stretchable display panel; and a second housing (130, 130A, 130B), comprising a second planar part and slidably disposed on the backplate (110, 110A, 110B), wherein the second housing (130, 130A, 130B) is adapted to abut against a second side of the stretchable display panel opposite to the first side, wherein the first housing (120, 120A, 120B) and the second housing (130, 130A, 130B) are adapted to move relative to each other to change a distance between the first housing (120, 120A, 120B) and the second housing (130, 130A, 130B), wherein a first sliding part is disposed on one of the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) at a place on which the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) are adapted to face each other, another one of the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) comprises a first guiding groove, and the first sliding part is adapted to pass through and slide within the first guiding groove, wherein a second sliding part is disposed on one of the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) at a place on which the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) are adapted to face each other, another one of the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) comprises a second guiding groove, and the second sliding part is adapted to pass through and slide within the second guiding groove, wherein the first planar part comprises a first border, the second planar part comprises a second border, the first border is complementary to the second border on a plane, and the first planar part and the second planar part are disposed on a side of the backplate (110, 110A, 1 10B) opposite to the accommodating space. a backplate (110, 110A, 110B), comprising an accommodating space, wherein the accommodating space is adapted to accommodate the electronic device; a first housing (120, 120A, 120B), comprising a first planar part and slidably disposed on the backplate (110, 110A, 110B), wherein the first housing (120, 120A, 120B) is adapted to abut against a first side of the stretchable display panel; and a second housing (130, 130A, 130B), comprising a second planar part and slidably disposed on the backplate (110, 110A, 110B), wherein the second housing (130, 130A, 130B) is adapted to abut against a second side of the stretchable display panel opposite to the first side, wherein the first housing (120, 120A, 120B) and the second housing (130, 130A, 130B) are adapted to move relative to each other to change a distance between the first housing (120, 120A, 120B) and the second housing (130, 130A, 130B), wherein a first sliding part is disposed on one of the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) at a place on which the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) are adapted to face each other, another one of the first housing (120, 120A, 120B) and the backplate (110, 110A, 110B) comprises a first guiding groove, and the first sliding part is adapted to pass through and slide within the first guiding groove, wherein a second sliding part is disposed on one of the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) at a place on which the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) are adapted to face each other, another one of the second housing (130, 130A, 130B) and the backplate (110, 110A, 110B) comprises a second guiding groove, and the second sliding part is adapted to pass through and slide within the second guiding groove, wherein the first planar part comprises a first border, the second planar part comprises a second border, the first border is complementary to the second border on a plane, and the first planar part and the second planar part are disposed on a side of the backplate (110, 110A, 1 10B) opposite to the accommodating space.