The invention discloses an elevator balance weight device, which is mounted on a lift car (6) of an elevator, wherein a servo electric cable (8) is set at the other side provided with a counter weight (7) set on one side relative to two sides of the lift car (6); an elevator balance compensation chain (5) is connected between the lift car (6) and the counter weight (7); the elevator balance weight device comprises a balance weight (4); the balance weight is located on one side relative to the counter weight (7) on the lift car (6); the balance weight (4) can be movably set on the lift car (6) relatively far away from and next to the balance weight (7); and a driving device is mounted on the lift car for driving the balance weight to move along the direction of being far away from and next to the counter weight (7). According to the invention, real-time balance to the reduction and increase in weight of a balance compensation beam can be realized, so unbalance loading of the lift car can be effective; abrasion to a guide device is reduced; and the comfort of a passenger who is taking the elevator can be improved at the same time.