A foldable supporting assembly includes an inner lateral bar unit, and first, second, third and fourth longitudinal bar units. The first and second longitudinal bar units are disposed at a first side, and rotatably connected with the first and second ends of the inner lateral bar unit. The third and fourth longitudinal bar units are disposed at a second side, and rotatably connected with the first and second ends of the inner lateral bar unit. When folded, one of the first and second longitudinal bar units is disposed between the inner lateral bar unit and the other one of the first and second longitudinal bar units, and one of the third and fourth longitudinal bar units is disposed between the inner lateral bar unit and the other one of the third and fourth longitudinal bar units.