PURPOSE: To micronize fine grains and uniformize the grain size by feeding fibers made of a thermoplastic resin and made thin to have a desired toner diameter, cutting the fibers at a length near the desired toner diameter, and micronize them.

CONSTITUTION: Multiple fibers are made thin to a desired toner diameter by a spinning device, they are spun into fiber bundles X and wound on bobbins 1a of a fiber feeding means 1. When a driving roller 1d is operated, the fiber bundles X are fed to the cutting die 2b of a cutting means 2. When a refrigerant is fed into a casing 2a from a refrigerant feeding system 3a by the action of a cooling means 3, the fiber bundles X, the cutting die 2b, and a rotary edge 2c in the casing 2 are cooled respectively into a low-temperature state. When the cutting means 2 is operated, the rotary edge 2c crosses the tips of the fiber bundles X protruded from the cutting die 2b, and the fiber bundles X are cut to manufacture cut fibers (toner fine grains).