Abstract: A porous ferrite core material for an electrophotographic developer, the porous ferrite core material including Mg in a content of 0.3 to 3% by weight, Ti in a content of 0.4 to 3% by weight and Fe in a content of 60 to 70% by weight, and the porous ferrite core material having a pore volume of 0.04 to 0.16 ml/g, a peak pore size of 0.4 to 1.6 ?m, a saturation magnetization of 40 to 80 Am2/kg, a remanent magnetization of less than 7 Am2/kg and a coercive force of less than 43 A/m; a resin-filled ferrite carrier for an electrophotographic developer obtained by filling a resin in the voids of the porous ferrite core material; and an electrophotographic developer using the ferrite carrier.