A Mn—Zn based ferrite sintered body containing 62 to 68 mol % of Fe2O3 and 12 to 20 mol % of ZnO is made to contain, as main constituents, NiO and/or LiO0.5. Additionally, a Mn—Zn based ferrite sintered body containing 62 to 68 mol % of Fe2O3 and 12 to 23 mol % of ZnO is made to contain, as additives, Si and Ca. This sintered body can achieve such properties that the saturation magnetic flux density at 100° C. is 450 mT or more (magnetic field for measurement: 1194 A/m), the minimum core loss value is 1200 kW/m3 or less (measurement conditions: 100 kHz, 200 mT), the bottom temperature at which the minimum core loss value is exhibited is from 60 to 130° C., and the initial permeability at room temperature is 700 or more.