An electrolytic treatment method and electrolytic treatment device are provided for electrolytic treatment of an aluminum web W by applying an alternating current to an upstream electrode and a downstream electrode disposed along a conveying direction a. At least one of a conveying velocity v of the aluminum web W, a frequency f of alternating current applied at the upstream electrode and the downstream electrode, and/or a web conveying direction separation distance d2 between the upstream electrode and the downstream electrode are set such that the alternating current and voltage waveform applied to the aluminum web W at the far end of the upstream electrode and the alternating current and voltage waveform applied to the aluminum web W at the near end of the downstream electrode do not reinforce each other.