PURPOSE: To obtain the titled slurry having an excellent stability at low cost with low power consumption, by using a specific improved mass colloider in producing a water slurry of a vegetable carbide to simultaneously conduct the pulverization and production of a slurry in one step.

CONSTITUTION: Vegetable carbides such as a charcoal and a used paper in an industrial waste which are indefinite solids are continuously pulverized for a long period of time with a mass colloider (melt crusher), which has been improved by providing a polymer-compounded vitrified grinder produced by compounding a vitrified grinder with a polymer to completely modify the material, to obtain a carbide having a particle diameter of 50μ or less. At the same time, to 1pt.wt. afore-mentioned carbide are added 0.8W1.2pts.wt. water and/or alcohol and optionally 1wt% or less (in terms of purified product based on the carbide) anionic or nonionic dispersant to obtain the titled slurry.