A resin-filled ferrite carrier for an electrophotographic developer filled with a silicone resin in voids of a porous ferrite core material which continuously extend from a surface to a core interior, wherein the resin-filled ferrite carrier has an average particle size of 20 to 50 .mu.m, and (Si/Fe).times.100 as determined from X-ray fluorescence elemental analysis is 2.0 to 7.0, and the particle size and (Si/Fe).times.100 are correlated, and wherein in the correlation relationship between [(Si/Fe).times.100] and the particle size, a gradient (a) in a correlation equation thereof is -0.50.ltoreq.a.ltoreq.0.15.