To improve maneuvering stability at rolling time of a vehicle by installing first/second lower rods pivoted so as to incline forward and obliquely upward by divergently inclining at an angle such as to satisfy a specific expression as they proceed backward.

First/second lower rods 34, 36 are respectively installed by divergently inclining as they proceed backward. An angle to a roller shaft of the first/second lower rods 34, 36 projected on a vertical plane containing the roller shaft connecting the roller center is denoted by θ1, a straight line distance up to the roller shaft from one end of the first/second lower rods 34, 36 is denoted by H, an interval between one end of the first lower rod 34 and one end of the second lower rod 36 is denoted by L and an angle to the first/second lower rods 36 and a longitudinal directional vertical plane projected on a horizontal plane is denoted by θ2. The angle θ1 and the angle θ2 at that time are set so as to satisfy an expression (0≤tanθ2.2H/L-tanθ1≤0.03).