PURPOSE: To improve the steering stability by constituting an FRP suspension arm so that the behavior of the tip due to the elastic deformation of the suspension arm may be appropriate, and optimizing the change of alignment due to the bound and rebound of wheels.

CONSTITUTION: The rear suspension is provided with a plate-shaped FRP arm body 32 which is fixed to a vehicle body on one end and connected to a wheel supporting member on the other end and a friction member 34 arranged in the arm body at the position to be offset downward of the neutral plane 36 of the arm body. The friction member is extended in an inclined manner to the width direction of the arm body along the neutral plane, abutted on the arm body on at least one surface to be separated in the direction offset from the neutral plane, and connected to the arm body on the other surface, and the Poisson ratio of the friction member in the plate thickness direction relative to the longitudinal direction of the arm body is larger than the Poisson ratio of the arm body.