A suspension device includes a pair of suspensions each containing at least one of a damping mechanism and a suspension spring. A tubular body-side member is on a vehicle body side. A tubular wheel-side member is on a vehicle wheel side and coupled to the body-side member, and moves relative to the body-side member in an axial direction. A hollow cylindrical cylinder is inside of the body-side member and the wheel-side member and includes a weak portion in the axial direction on an outer side. A rod member is inside of the body-side member and the wheel-side member and moves relatively in the axial direction in accordance with movement of the body-side member and the wheel-side member. A first defining member secured to an end portion of the rod member and in contact with the cylinder movably in the axial direction of the cylinder defines space in the cylinder.