Seat leg lifting device

The utility model discloses a seat leg lifting device. The chair comprises a chair seat unit, a support plate, a connecting rod unit, a damper, a first spring and a second spring, the connecting rod unit is driven by external force to drive the supporting plate to be switched between the folding position and the leg lifting position. The damper is installed at the pivot position of the first connecting rod and the third connecting rod. Rotation damping is provided when the second connecting rod and the third connecting rod relatively pivot; the first spring and the second spring are connectedbetween the chair seat unit and the connecting rod unit; the elastic coefficient of the first spring is larger than the elastic coefficient of the second spring, the free length of the first spring islarger than the free length of the second spring, and when the supporting plate is located at the folding position, the elastic force and the stretching length of the first spring and the second spring are the maximum values.