To provide a device for preventing a belt meandering motion with a simple structure that carries out a papermaking process for papermaking waste pulp in high reliability with little disorders, in a wastepaper recycling apparatus of a fixture size capable of being installed in the room of a small scale shop and the like.

A rolling contact roller 140 is constructed to contactingly roll in a state to give a tension to the net-like belt 105 of a papermaking net conveyor part 95 for treating and conveying waste paper pulp, and a roller swinging part 141 is constructed to swing the rolling contact roller 140 crosswise to the traveling direction of the net-like belt 105. When a traveling position of the net-like belt 105 is in a proper travel range, the rolling contact roller 140 is constructed to be held in a neutral position to be perpendicular to the travel direction of the net-like belt 105, while when the travel position of the net-like belt 105 is out of the proper travel range, the rolling contact roller 140 is constructed to face to the direction for repairing the meandering motion in which the travel position of the net-like belt 105 is moved into the proper travel range.