To improve material yield so as to reduce cost in a suspension arm made of sheet metal formed of an arm body and a reinforcing member connected to the arm body in such a way as to form a box-shape cross section.

A reinforcing member is divided into a plurality of reinforcing pieces 2, 3 so as to be able to blank these reinforcing pieces 2, 3 at a good yeild in a blank space of a blanked part of an arm body 1. The arm body 1 is formed into approximately U-shape cross section, and the reinforcing pieces 2, 3 are formed in approximately plate shape. In the case of an L-shape suspension arm, the respective reinfrocing pieces 2, 3 are formed in tapered shape toward an arm end part so as to facilitate blanking of the reinforcing pieces 2, 3.