The invention discloses an in-built component for an automobile. The in-built component for the automobile is provided with an impact absorbing body arranged at the inner side of the side panel chamber of the automobile, and can enhance the impact absorbing performance by improving the shape and the structure of the impact absorbing body capable of absorbing impact load on the basis of bending deflection when side impact occurs. One side of the impact absorbing body (30) at the back side of an impact area (IA) of the in-built component for the automobile (10), i.e. a door panel, is provided with an opening (31), and the other side of the impact absorbing body (30) is provided with a hollow box body with a bottom wall (32); and the four corners of the bottom wall (32) are provided with corner cutting parts (34), chamfering is carried out on the turning parts of a side wall (33) to form chamfer parts (333) and form slot parts (334) for occlusion or triangular fins (36) or inner fin (321) and the like, thus regulating the reacting force when side impact occurs and further improving the impact absorbing performance.