A belt unit includes an endless belt, a plurality of support rotators, a pair of supports, and a stopper. The endless belt is wound around the plurality of support rotators. The pair of supports extend in a direction intersecting an axial direction of each of the plurality of support rotators. The pair of supports are disposed opposite to and spaced away from each other, to rotatably support both ends of each of the plurality of support rotators in the axial direction. The stopper is disposed at at least one end of at least one support rotator of the plurality of support rotators and outside from a corresponding one support of the pair of supports in the axial direction, to restrict movement of the corresponding one support in the axial direction.