An apparatus for the electrolytic treatment of the product L using a treatment agent is used to make the treatment of a plate-shaped product more uniform. This apparatus includes: devices for retaining 40, 42 the product L in the apparatus, one or a plurality of flow devices 10, which each include at least one nozzle 15 and are disposed situated opposite the product L, one or a plurality of counter electrodes 30, which are inert relative to the treatment agent and are disposed parallel to at least one treatment surface, means for generating a relative movement 44 between the product L, on the one side, and the flow devices 10 and/or the counter electrodes 30, on the other side, in at least one direction parallel to a treatment surface. The product L can be immersed into the treatment agent during the treatment.