a method of producing copper powder is provided that uses electrolytic cuprous oxide as the starting material for the production of copper powder suitable for a conductive filler whose particles have an average particle diameter of not greater than 1 μm or even not greater than 0 . 5 μm and are of uniform size . in one aspect , the method comprises a step of mixing cuprous oxide with a reducing agent in a liquor in which a protective colloid is present and to which a water - soluble copper salt has been added and in another aspect comprises a step of reducing a water - soluble copper salt in a liquor in which a protective colloid is present , thereby forming a slurry , and a step of reducing cuprous oxide in the presence of the slurry . as the water - soluble copper salt can be used , for example , 0 . 1 - 20 moles of a monovalent copper salt such as cuprous chloride per 100 moles of the cuprous oxide . as the protective colloid can be used 1 - 40 parts by mass of a water - soluble polymer per 100 parts by mass of the cuprous oxide .