A ferrite carrier core material for an electrophotographic developer, wherein: a ferrite composition contains 0.5 to 2.5% by weight of Sr; and a presence amount of Sr-Fe oxides satisfies the following conditional expression 0 < a weight of a Sr ferrite / a total weight of all Sr-Fe oxides ≤ 0.8 provided that the total weight of all Sr-Fe oxides = the Sr ferrite + the Sr-Fe oxides other than the Sr ferrite, wherein the weight of the Sr ferrite and the total weight of all Sr-Fe oxides are determined by X-ray diffractometry as measured according to the description; in the distribution in the number of the shape factor SF-2, the number of particles of 100 or more and less than 105 is 40% by number or more; that of 105 or more and less than 110 is 5 to 40% by number; that of 110 or more and less than 120 is 20% by number or less; that of 120 or more is 10% by number or less; and that of 130 or more is 5% by number or less; the BET specific surface area is 0.15 to 0.30 m 2 /g; the average particle diameter D 50 in measurement by a laser diffraction type particle size distribution analyzer is 20 to 35 μm; the magnetization by VSM measurement when a magnetic field of 11000/4π·kA/m is impressed is 50 to 65 Am 2 /kg, wherein the magnetization is measured using a vibrating sample-type magnetometer, model name: VSM-C7-10A, made by Toei Industry Co., Ltd., a measuring sample is filled in a cell of 5 mm in inner diameter and 2 mm in height, and set on the magnetometer, the measurement is carried out by impressing a magnetic field and sweeping the impressed magnetic field to 398 kA/m (5 kOe), the impressed magnetic field is reduced, and a hysteresis curve is fabricated on a recording paper, and the magnetization at an impressed magnetic field of 80 kA/m (1 kOe) is read out from data of the curve, and the ferrite carrier core material comprises 15 to 22% by weight of Mn, 0.5 to 3% by weight of Mg, and 45 to 55% by weight of Fe. a ferrite composition contains 0.5 to 2.5% by weight of Sr; and a presence amount of Sr-Fe oxides satisfies the following conditional expression 0 < a weight of a Sr ferrite / a total weight of all Sr-Fe oxides ≤ 0.8 provided that the total weight of all Sr-Fe oxides = the Sr ferrite + the Sr-Fe oxides other than the Sr ferrite, wherein the weight of the Sr ferrite and the total weight of all Sr-Fe oxides are determined by X-ray diffractometry as measured according to the description; in the distribution in the number of the shape factor SF-2, the number of particles of 100 or more and less than 105 is 40% by number or more; that of 105 or more and less than 110 is 5 to 40% by number; that of 110 or more and less than 120 is 20% by number or less; that of 120 or more is 10% by number or less; and that of 130 or more is 5% by number or less; the BET specific surface area is 0.15 to 0.30 m 2 /g; the average particle diameter D 50 in measurement by a laser diffraction type particle size distribution analyzer is 20 to 35 μm; the magnetization by VSM measurement when a magnetic field of 11000/4π·kA/m is impressed is 50 to 65 Am 2 /kg, wherein the magnetization is measured using a vibrating sample-type magnetometer, model name: VSM-C7-10A, made by Toei Industry Co., Ltd., a measuring sample is filled in a cell of 5 mm in inner diameter and 2 mm in height, and set on the magnetometer, the measurement is carried out by impressing a magnetic field and sweeping the impressed magnetic field to 398 kA/m (5 kOe), the impressed magnetic field is reduced, and a hysteresis curve is fabricated on a recording paper, and the magnetization at an impressed magnetic field of 80 kA/m (1 kOe) is read out from data of the curve, and the ferrite carrier core material comprises 15 to 22% by weight of Mn, 0.5 to 3% by weight of Mg, and 45 to 55% by weight of Fe.