Kaolin minerals are used as filler and coater in paper manufacturing. In recent years the natural resources of kaolin of good quality have diminished in this country, thus necessitating the import of raw materials and products from Soviet Russia, the United States of America and some other countries.It is considered desirable that filler and coater should contain 35∼65% of -2μ particles and 70∼90% of -2μ particles, respectively.It is also desirable that the whiteness degree should be high, the suspension viscosity be low, and the abrasiveness of the screen and the cutter for paper manufacturing be low.We conducted the wet attrition-grinding of coarse kaolin minerals of low quality by making a tentative attrition-grinding machine in order to make use of the effectiveness of domestic kaolin resources, and investigated the nature of the ground material in terms of particle size distribution.In other words, we conducted the wet attrition-grinding of domestic coarse kaolin materials and studied its effects on particle size distribution of the ground material of attrition-grinding time, initial concentration, rotor's rotating numbers, and the quantity of the medium.As a result, d50≈1.5μ kaolin minerals were obtained by increasing the rotating numbers of the rotor and the quantity of the medium, and decreasing the quantity of raw materials.The observation by the use of an electron microscope shows that coarse kaolin minerals are stacked, and that they seem to get detached by attrition-grinding.We studied also the abrasiveness of the material of an attrition-grinding machine and the consuming power.In this experiment it became evident that stainless steel (SUS 27), nitriding steel, vinyl chloride, rubber, nylon and polypropylene as metallic and organic materials were resistant to abrasion, respectively.The abrasiveness of spherical glass particles used as medium is extremely low.The power needed for the attrition-grinding from 6.2μ kaolin to 1.5μ is about 400watt/kg kaolin.From the above results, we conclude that the wet attrition-grinding of kaolin minerals are industrially feasible.