PURPOSE:To improve the corrosion resistance of a deposited magnetic medium and to make it possible to form a magnetic layer enabling high density recording and reproducing by simultaneously adding a rhenium salt and a zinc salt to a magnetic plating soln. contg. a cobalt salt, a complex forming compd., a reducing agent and a pH adjusting agent. CONSTITUTION:A rhenium salt and a zinc salt are simultaneously added to an aq. soln. contg. a cobalt salt or a cobalt slat and a nickel salt, a compd. forming a complex with the metallic salts, e.g., tartaric acid, a reducing agent for the metallic salts and a pH adjusting agent to prepare a magnetic electroless plating soln. When the plating soln. is used, a formed magnetic layer has improved resistance to corrosion by pure water, hydrochloric acid and sulfuric acid, an increased S-N ratio and other effect.