A lifting device comprises a bias sliding seat, a lifting arm and a braking device. The bias sliding seat is suitable for sliding relative to a component of a structural body capable of being opened, the lifting arm is provided with two ends, one end of the lifting arm is suitable for being connected with the component of the structural body in a pivotal mode, and the other end of the lifting arm is connected with the sliding seat. The braking device comprises at least one braking seat capable of sliding on the corresponding braking faces of the lifting device, and force generated by bias pressure on the bias sliding seat is adjusted by the braking device. An adjusting device is suitable for progressive adjustment on the force generated by bias pressure on the bias sliding seat, an operation component is included, and when the operation component is operated by a user, the adjusting device is started to adjust braking force, exerted to the braking faces, of the braking seat at the specific position of the braking seat.