A suspension device according to one embodiment of the present disclosure which is equipped with an upper arm which is supported by a knuckle of the vehicle wheel so as to be capable of oscillation, and also supported by a side member which extends in the vehicle front-rear direction so as to be capable of oscillation, wherein: the upper arm has a tip end section positioned at the outside end in the vehicle widthwise direction, and also has arm sections which fork from the tip end section toward the inside in the vehicle widthwise direction; and the upper arm is formed in a manner such that the cross-sectional area of one arm section is greater than the cross-sectional area of the other arm section.