PURPOSE: To realize simplification of pretreatment process, reduction in cost, and simplification of waste water treatment of an electroless plating method.

CONSTITUTION: A material to be plated is treated at the temp. as high as about ≥80°C with a soln. containing a tervalent iron ion and bivalent metal ions which can form a ferrite magnetic material with the iron ion. Then the material is neutralized to precipitate the ferrite and then treated in an electroless plating bath. Thus, the man-hour and the cost can largely be reduced. Advantages are that low-purity water can be used, the waste water treatment is simplified, the plating time is short owing to high temp. treatment, and that the obtd. plating film has high strength and large shielding effect against electromagnetic waves.