An upper arm in a suspension system for a vehicle includes a substantially plate-like body portion which is bifurcated in a longitudinal direction of a vehicle body from a tip end side of the upper arm connected to a knuckle toward a base end side of the upper arm connected to a vehicle body frame, an outer flange extends downwardly from an outer edge of the body portion and then extends outwardly, and an inner flange extends downwardly from an inner edge of the body portion and then extends inwardly. The body portion and the outer and inner flanges are integrally formed from a single material blank through pressing. The vertical dimension of the inner flange closer to load application lines which connect a mounting hole for a ball joint for connecting the upper arm to a knuckle with mounting holes for a pair of rubber bush joints for connecting the upper arm to a vehicle body frame is larger than the vertical dimension of the outer flange farther from the load application lines. Thus, it is possible to increase the rigidity of the upper arm and reduce the weight thereof in comparison to known upper arms with similar bifurcated structures.