To provide a roller unit which is detachably attached to an automotive excavator.

The roller unit includes a roller 1, a base plate 2 having the roller 1 mounted on a lower surface thereof, and a mounting portion 5 for pinching a front wall 4a of an excavating bucket of the automotive excavator 3, from above and below, in a manner maintaining the horizontal position of the front wall 4a. Then, the roller 1 is rendered detachably attachable to the bucket 4 with its rotation shaft extending in a lateral direction of the bucket 4. Thus, without using an expensive dedicated automotive vehicle, compaction of the ground 7 after backfilling can be efficiently carried out.