PURPOSE: To improve reaction resistance and durability and to reduce the production cost of a tool material for firing of a soft ferrite compsn. having a spinel structure by using a material containing MgO.Al2O3 as the main component and ZrO2 as the subcomponent.

CONSTITUTION: This tool material contains 85-99.5wt.% MgO.Al2O3 as the main component and 0.5-15wt.% ZrO2 as the sub component. Compared to a tool material comprising alumina or alumina-mullite, the obtd. material causes no irregular shrinkage in the ferrite nor such a problem that SiO2 reacts with the ferrite to damage the crystal of the ferrite and to deteriorate the characteristics of the ferrite. Since the obtd. material contains ZrO2, it is excellent in durability and inexpensive compared with a material comprising zirconia or magnesia. Since the obtd. material contains one or more elements of the metal elements which are present in the soft ferrite having a spinel structure, and since the material contains ≤5wt.% compsn. of the same spinel structure as the ferrite, no influence of movement of the component from the ferrite to the tool material is caused, which means any pretreatment is not necessary.