To make it possible to highly precisely manage a clearance between a shackle and a stopper without the necessity of upgrading dimensional precision of each component and strictly managing assembling precision.

A suspension system has a front bracket 3 and a rear bracket 4 disposed at positions in front of and behind an axle 2 of a side rail 1, has the front end of a leaf spring 5 pivoted on the front bracket 3, has the rear end of the leaf spring 5 pivoted on the rear bracket 4 via a shackle 6 that can be freely slid back and forth, and has the axle 2 suspended in the intermediate part of the leap spring 5. The suspension system includes a stopper 13 that restricts backward sliding of the shackle 6, which transcends a normal use range, in a case that the leaf spring 5 is broken on a front side beyond the intermediate part thereof, and adjustment means 14 that is disposed in a region of the stopper 13 opposed to the shackle 6 and adjusts a clearance between the shackle 6 and stopper 13.