A upper arm 4b of a suspension for a vehicle is constructed by: a casing 12 that is supported by the vehicle so as to be able to pivot in the up-down direction; a pair of screw shafts 20 that are supported by the casing 12 so as to be able to move only in the axial direction; a pair of screw nuts 21 that engage around the pair of screw shafts 20, and are supported by the casing so as only to be able to rotate; a worm reduction gear 14 that rotates the screw nuts 21; and a pair of link arms 29, where the base end sections respectively connect to the tip end sections of the pair of screw shafts 20 and the tip end sections respectively connect to knuckle 3 so as to be able to rotate around a shaft in the up-down direction of the vehicle. The screw shafts 20 are moved out in opposite directions from each other in the axial direction, which causes the opening angle of the pair of link arms 29a to change, and thus changes the overall length of the upper arm 4b in the width direction of the vehicle.