A composite medium and method thereof for simultaneous removal of cationic and anionic heavy metals are provided to remove cationic and anionic heavy metals effectively. The method includes dissolving sodium alginate powder into deionized water to provide an alginate solution, and introducing amine group-supported mesoporous iron oxide and synthetic zeolite into the alginate solution and kneading the resultant mixture. The method also includes adding the alginate solution mixed with the mesoporous iron oxide and synthetic zeolite dropwise to an aqueous calcium chloride solution so that each drop of alginate solution is cured to form a bead-like composite medium, and vacuum drying the bead-like composite medium to remove water present in the composite medium, while the mesoporous iron oxide and synthetic zeolite are moved from the inside of the composite medium toward the surface of the composite medium.