To secure the moving capability on a passage in a bus cabin and lower the floor surface satisfactorily.

A cross-beam 23 is coupled with the tail of a vertical frame 21 installed in the fore-and-aft direction of a bus body, and a bracket assembly 25 is installed at each end of the cross-beam 23 while a rear bracket assembly 38 is installed at each end of a rear cross-beam 35 confronting the cross-beam 23, wherein a pair of side frames 43 and 44 are installed opposingly between fenders for the two rear wheels with the passage interposed in such a way as set overhead between the bracket assembly 35 and the rear bracket assembly 38, and between these 35 and 38 a rear suspension 70 is installed overhead. The load from the rear suspension 70 is strongly received by the two bracket assemblies 35 and 38 so that the load applied to the side frames 43 and 44 is reduced, and it is possible to make fine setting of the side frames 43 and 44 to be located opposingly with the passage interposed, which enables securing the effective width of passage and facilitates moving on the passage.