PURPOSE: To improve fluidity, to rapidly disperse a replenished toner uniformly, and to enable uniform triboelectrification by using a magnetic carrier obtained by uniformly attaching to the surface of each thermoplastic resin particle, a large number of magnetic particles smaller in diameter than the resin particle.

CONSTITUTION: Thermoplastic resin particles 2, 13 in the lower figure, made of acrylic resin, polystyrene, or the like and magnetic particles 3, 14 in the lower figure smaller in diameter than the particles 2 are introduced into a roll bottle 11, and the particles 14 are uniformly attached to the surfaces of the particles 13 by rotating the bottle 11 at a temp. a little lower than the m.p. of the particles 13. The magnetic carrier 1 thus obtained is low in sp.gr. and good in fluidity, and it can disperse a toner in a short time, and it can be triboelectrified uniformly. Since the particles 3 are attached by utilizing the friction heat of the particles 2, 3 being rotated and mixed, each particle 2 is kept in a state of a good spherical form without being deformed.