A suspension system comprising a pair of fiber reinforced plastic spring arms, right and left, and a beam assembly connecting the respective free ends of the arms, said springs arms having a free-end-side portion and being vertically bendable, each spring arm serving as a suspension spring. A fixed end of each spring arm is fixed to a vehicle body. The beam assembly, which extends in the transverse direction of the vehicle body, includes an intermediate beam member of fiber reinforced plastic and metallic end beam members fixed individually to two opposite end portions of the intermediate beam member. Each end beam member is provided with an axle. If the right and left spring arms are subjected to loads of opposite phases at the time of turning, the intermediate beam member is twisted to produce a stabilizer effect.