To provide a method for producing a wastepaper pulp, by which the wastepaper pulp excellent in folding endurance and suitable for a paper, paperboard, etc., is produced in the coexistence of an improving effect of durability of the paper, and drainage by blending a specific long fiber fraction with a micro-fibrilated fiber.

This method for producing a wastepaper pulp comprises the step of carrying out a classification treatment of a wastepaper pulp regulated so that the difference of Canadian standard freenesses between the wastepaper pulp before the classification treatment and a long fiber fraction after the classification treatment may be 50-250 ml, preferably 80-200 ml to remove a short fiber fraction and to obtain a long fiber fraction, and the step of blending a micro-fibrilated fiber of preferably 1-10 wt.% with the long fiber fraction to provide the objective wastepaper pulp.