Abstract: A grinder for use in a grinding apparatus, comprising a pair of rotary and stationary discs facing each other, in which the rotary disc is rotated through a shaft by a drive motor, and in which a large number of grinding material particles are embedded in the surface of the discs to form microbites to grinding surfaces of the discs, and the strength of the grinding surface of the stationary disc is inferior to that of the rotary disc. The grinding is accomplished by fine cutting which is carried out by microbits formed of superhard grinding material particles having a sharp edge, rather than by mashing or abrasion. The grinder is formed as a cassette type so as to be replaced readily and quickly by new one. The grinder is provided with a clearance adjustor for adjusting the clearance between the rotary disc and the stationary disc.