An electric seat and an angle adjustment device thereof are provided. The angle adjustment device includes an inner toothed plate and an outer toothed plate engaging with each other, and an eccentric cavity formed therebetween. An eccentric ring completely occupying a positive eccentric region of the eccentric cavity is provided in the eccentric cavity. The eccentric ring has a first accommodating region and a second accommodating region along a circumferential direction. The angle adjustment device further comprises a driving component for driving rotation of the eccentric ring. A damping component is provided in the first accommodating region and/or the second accommodating region, and the damping component is in a compressed state during operation of the driving component. The damping component eliminates a useless stroke in the above operation, thereby eliminating an adjustment lag experienced by a passenger during reverse adjustment of a seat and backrest.