To simplify an axle sheet by offsetting the positional relation in a support beam among the part to be connected to the front side air spring of a rear axle, the part to be supported on the wheel side of a housing, and the part to be connected to the rear air spring of the rear axle.

A support beam 109 is formed into substantially a flat arch form by connecting lower end side connecting parts 109a, 109b to each air spring 2a, 2b arranged in the front and rear of a wheel along car body longitudinal direction. The connecting and supporting part of a rear axle housing 4 is offset substantially in the lateral direction of the car body, and the connecting and supporting position is situated in a rear axle housing end part 4a formed of a simple surface. In the support beam 109, since the connecting and supporting part is offset substantially in the lateral direction, and the connection and support area performed in the simple surface of the rear axle housing end part 4a, upper and lower axle sheets 105, 106 can be simplified.