To provide a method for preventing soil formed in a papermaking process to realize the papermaking process excellent in operability.

This method for preventing the soil is to use bentonite and a coagulant in the papermaking using waste paper pulp from which at least 0.5 wt.% hydrophobic substance based on the solid portion of the pulp is solvent-extracted. Preferably, the coagulant is a cationic polymer, and further preferably the coagulant is a diarylamine-based polymer. As another preferable form of the method for preventing the soil, the anionization degree of the bentonite at pH 9 is 0.2 to 1 meq/g by solid content, the coagulant and bentonite are added by 10 to 2,000 ppm and 100 to 10,000 ppm, respectively, based on the solid portion of the pulp slurry, and releasing rate is as at least 85%.