The present invention relates to an apparatus for dialysis treatment which has device(s) for balancing fresh and used dialysis fluid. The present invention also relates to a method of balancing fresh and used dialysis fluid. The apparatus and method according to the present invention for balancing fresh and used dialysis fluid are characterized in that the individual balancing chambers of the balancing system receive both fresh dialysis fluid and used dialysis fluid, the functions of the balancing chambers being alternately interchanged. In this way, exact balancing can be achieved even when the volumes of the individual chambers differ from one another. Over the period of the treatment as a whole, the differences between the volumes balance each other out due to the cyclic interchange of the chambers.
