A potential fall created by a space‐charge dipole layer that moves as a solitary wave with a velocity close to that of an electron in the positive column at higher pressure in oxygen is shown. Sometimes only one potential fall exists between electrodes. The number of the potential fall changes with discharge current, by which the hysteresis phenomenon is found. Since the width of a potential fall is much larger than the electron mean‐free path, both ionization and attachment play an important role in the potential fall for the formation of a dipole layer. The shape of the small current change when a dipole layer arrives at an anode is examined, suggesting what is existent in a dipole layer. The nature of the self‐excitation of a dipole layer in the positive column cannot be found. The reason why a dipole layer appears and how it is maintained in the positive column of the oxygen glow discharge are explained.