A process for producing a magnetic recording medium which comprises forming on a non-magnetic substrate a magnetic thin layer composed of columnar crystal particles comprising Co, or Co and Ni and/or Cr by vapor/depositing the metal atoms at an angle of incidence of at least 20.degree. relative to the normal line of the principal plane of the substrate, and then forcibly oxidizing the magnetic thin layer by electrochemical treatment to form an oxide layer on the surface of the columnar crystal particles of the magnetic thin layer, and thereby to form a magnetic layer.