A magnetic core has a structure in which alloy phases 20 each including Fe, Al, Cr and Si are dispersed and any adjacent two of the alloy phases 20 are connected to each other through a grain boundary phase 30. In this grain boundary phase 30, an oxide region is produced which includes Fe, Al, Cr and Si, and includes Al in a larger proportion by mass than the alloy phases 20. This magnetic core includes Al in a proportion of 3 to 10% both inclusive by mass, Cr in a proportion of 3 to 10% both inclusive by mass, and Si in a proportion more than 1% and 4% or less by mass provided that the sum of the quantities of Fe, Al, Cr and Si is regarded as being 100% by mass; and includes Fe and inevitable impurities as the balance of the core.