Abstract: Peritoneal dialysis device (10) with a balancing chamber (28), which is divided into two balancing chamber halves (32 and 34) by a membrane (30), with an introduction line arrangement (16, 20, 22, 24), a discharge arrangement (22, 24, 20, 62), a catheter line arrangement (36, 38, 42), a valve arrangement (46-52), a pump arrangement (60, 108, 110) and a control unit (82), which switches the balancing chamber halves (32 and 34) in the filling or emptying operation with the aid of the valve arrangement (46-52).The peritoneal dialysis device (10, 106) operates under pressure monitoring volumetrically in the filling phase and pressure-controlled in the emptying phase, and determines the volume of dialysis fluid introduced or discharged from the number of balancing chamber strokes and the ultrafiltration volume from the difference of these.