A rubber spring device is formed by alternately laminating a plurality of layers of hard plates whose linear dimension W in a direction parallel to the longitudinal direction of each equalizer bar is shorter in plan view than a linear dimension H in a direction parallel to an axle direction, and rubber layers. The rubber spring device is disposed between an end portion of each equalizer bar and a center axle in an articulated dump truck, and is allowed to function as a suspension. Thus, even when the rubber spring device is deformed into an accordion shape, peak positions of an internal stress within each rubber layer can be dispersed and reduced, thereby preventing generation of cracks within each rubber layer.