To provide a slurry-conveying system capable of preventing a pipeline clogging trouble caused by staying slurry from occurring.

The slurry-conveying system conveys slurry from a slurry relay tank 1 via conveying pipeline 4 and a slurry service tank 2 to a kneader 3 by operating a slurry transferring pump 5 and a slurry feeding pump 6, where the system is equipped with a large circulation pipeline 11 for returning the slurry from the upperstream side close to the kneader 3 to the slurry relay tank 1, small circulation pipelines 13 and 14 for returning the slurry from the respective downstream side of the slurry relay tank 1 and the slurry service tank 2 to these tanks, viscometers 20-1 and 20-2 for measuring the viscosity of the slurry flowing through the conveying pipeline 4 between the branching part to the small circulation pipeline 13 and the slurry service tank 2 and between the branching part to the small circulation pipeline 14 and the kneader 3, respectively, and a controlling part 30 for controlling the system to carry out a large circulation operation for flowing the slurry via the large circulation pipeline 11 when the slurry viscosity detected by the viscometers is equal to or higher than a predetermined value.