Disclosed herein is an LC aligning agent using diamine having dendron side chains. In detail, the present invention relates to a composition for an LC alignment film which employs diamine having dendron side chains to produce polyamic acid, followed by imidization. When the LC alignment film is applied to a liquid crystal display device, high heat resistance, high penetration in a visible ray range, excellent alignment, and a high voltage holding ratio are assured. Even though it contains a small amount of functional diamine, a high pretilt angle can be assured. Thus, the pretilt angle is easily controlled and a vertical aligning force is improved.