A ferrite core comprising a sintered oxide containing at least 48.6 to 53.9 mol % of Fe on Fe.sub.2O.sub.3 basis, 12.3 to 35.2 mol % of Ni on NiO basis and 16.4 to 37.0 mol % of Zn on ZnO basis as metal elements, and contains a crystal phase comprising two or more kinds of solid solutions selected from NiFe.sub.2O.sub.4, ZnFe.sub.2O.sub.4 and FeFe.sub.2O.sub.4, wherein full width at half maximum of a diffraction peak, of crystal phase of which diffraction angle 2.theta. is in a range from 34.6 to 36.4.degree. as measured by X-ray diffraction analysis using Cu--K.alpha. beam, is 0.4.degree. or less.