The present invention provides a Mn—Zn ferrite having an electrical resistivity exceeding 1 &OHgr;m order and having a low core loss in a high frequency region exceeding 1 MHz. The basic component composition of the Mn—Zn ferrite includes 44.0 to 49.8 mol % Fe2O3, 6.0 to 15.0 mol % ZnO (15.0 mol % is excluded), 0.1 to 4.0 mol % at least one of TiO2 and SnO2, and remainder MnO, wherein desired results are obtained by limiting Fe2O3 content to less than 50 mol % that is the stoichiometric composition and adding a proper amount of TiO2 or SnO2 and further controlling its average grain size to less than 10 &mgr;m.