PURPOSE: To obtain a superior electrophotographic developer which has excellent gradational reproducibility by mixing toner which is decreases relatively in electric resistance by incorporating pigment at a specific ratio with ferrite carriers having a specific particles size distribution.

CONSTITUTION: Electrodes 6 are fitted at both sides of the 10mm gas of a magnet 1 which generates a 1,500 gauss magnetic field, and 300mk carriers 2 are put between them to form a bridge with a magnetic field. A voltage is applied between the electrodes 6 and 6 at both sides and when the sectional area of the bridge, a voltage, and a current read simultaneously on a voltmeter 4 and an ammeter 5 are denoted as Scm2, V, and I (A), carrier resistance is VS/I. Then, ferrite carriers which are relatively small in said resistance value and have such a particle size distribution that the rate of 100W300 meshes is ≥900wt% and toner whose pigment content rate is ≥300wt% are mixed to obtain the developer. Thus, the developer having excellent gradational reproducibility is obtained.