A 0.1 to 0.5 mm-thick plated steel sheet having high coercive force and magnetic flux density is provided by hot rolling a slab comprising by weight carbon: 0.01 to 0.09%, silicon: not more than 1.0%, phosphorus: not more than 0.3%, manganese: not more than 1.5%, sulfur: not more than 0.04%, aluminum: not more than 1.0%, and nitrogen: not more than 0.01% with the balance consisting of iron and unavoidable impurities, cold rolling the hot rolled sheet, annealing the cold rolled sheet to prepare a steel sheet having an average grain diameter of 3 to 15 .mu.m, temper rolling the steel sheet with a reduction ratio of not more than 3%, and plating the temper rolled sheet with chromium or nickel. This enables the provision of a magnetic shielding material having no significant drift and very good electron beam landing properties.