A lifting device for lifting a table includes two legs, each of the legs includes a pneumatic assembly and an inner rod, the pneumatic assemblies are disposed in the legs, and the inner rods are inserted in the legs and connected to the pneumatic assemblies, so that the pneumatic assemblies drive the inner rods to move up and down. A synchronization mechanism is disposed between the two legs, and has two ends connected to the inner rods by two connecting assemblies, so that the inner rods are driven by the synchronization mechanism to lift or lower the tabletop in a synchronous manner, the synchronization mechanism includes: a cable control unit and a clutch unit controlled by the cable control unit, the cable control unit includes a control handle and a cable which is disposed at the bottom of the tabletop.