PURPOSE: To enhance the supporting rigidity by forming fastening portions, which are spaced apart from each other in the back-and-forth direction of an automotive vehicle, with respect to brackets fastened to the underside of a side member and pivotally attaching a suspension arm between two support portions formed between the two fastening portions.

CONSTITUTION: A recessed portion 5, which is concaved upwards, is formed on the underside of a side member 1 of an automotive vehicle. A suspension member 2, which is formed with a convex portion 6, is disposed at a lower position of the side member 1 and, a recessed portion 7, which is recessed upwards, is formed on the underside of the member 2. A suspension-arm attachment bracket 3 is composed of tapered brackets 3a having a hat-shaped section and retainers 3b, 3c having an L-shaped section. The bracket 3a is disposed in corresponding relation to the recessed portion 7 on the underside of the suspension member 2 and those elements 1 to 3 are fastened together by means of bolts. And a cylindrical portion formed on a suspension arm 4 is disposed in corresponding relation to bolt holes formed in the front and rear walls of opposed sides of the retainers 3b, 3c and in the front and rear walls of the opposed brackets 3a, for bolt fastening.