Abstract: A method for forming a metallic mirror surface on a receiving surface, comprises the steps of cleaning the receiving surface to be coated with a metallic mirror surface; spraying on the receiving surface an activating treatment agent containing stannous chloride and at least one precious metal salt of palladium, gold and silver or the like; and separately spraying concurrently on the receiving surface, a reacting metallic salt solution and a reducing agent solution to form the metallic mirror surface. The method may include the step of treating the receiving surface with a water wash treatment. The activating treatment agent may be in a solution form and contain about 10 cc to about 44 cc of hydrochloric acid, about 1.5 g to about 5 g of stannous chloride and about 0.001 g to about 0.005 g of palladium chloride per 1 liter of water.