The invention provides a vibration damping device. The vibration damping device comprises a connecting body, a planar connecting-rod mechanism and a hanging assembly with the preset weight. The connecting body is used for being connected with an electric transmission line; the planar connecting-rod mechanism is composed of at least three connecting rods which are sequentially and rotationally connected, and the two connecting rods arranged at the two ends of the planar connecting-rod mechanism are both rotationally connected with the connecting body; the hanging assembly is connected with the planar connecting-rod mechanism. When the vibration damping device is used, the connecting body is connected with the electric transmission line; when the electric transmission line swings, the electric transmission line drives the planar connecting-rod mechanism and the hanging assembly to jointly move; as the hanging assembly has the certain weight, the hanging assembly has the inhibiting effect on swinging of the electric transmission line, and the line fault problem caused by swinging of the electric transmission line is solved; in addition, compared with an existing deicing anti-swinging mode of an electric transmission line, as the vibration damping device is mainly composed of the planar connecting-rod mechanism, the structure is simple, implementation is easy, and cost is low.