PURPOSE: To obviate the generation of deficient curing in spite of electron ray irradiation in the atm. by executing the electron ray irradiation in the atm. then irradiating UV rays.

CONSTITUTION: A magnetic paint prepd. by incorporating a compd. having radiation-polymerizable carbon-carbon double bonds as at least one component of a binder into said part is coated on a base and thereafter the electron rays are irradiated thereon and the UV rays are further irradiated thereon after said irradiation. The radicals formed by the irradiation of the electron rays more effectively than by the UV rays transform once to peroxy radicals by reacting with the oxygen in the atm. but are converted to the original radicals by the subsequent irradiation of the UV rays. The attach reaction with the carbon-carbon double bonds is thus remarkably accelerated.