The invention aims to provide a compact peritoneal dialysis apparatus using a disposable cassette integrally formed with a diaphragm and heating portion, in which a flow path can be switched quietly and a heating ability is high. By using a disposable cassette (8) integrally formed with a diaphragm, heating portion, and flow path switching portion, a predetermined amount of dialysis fluid is heated to a predetermined temperature with the heating portion. Clamps (111 - 118) for opening/closing a flow path switching portion are provided in order to form flow paths through which the heated peritoneal dialysis fluid is distributed into the peritoneal cavity of a patient almost continuously and is sucked and drained from the peritoneal cavity of the patient. The invention also aims to provide a peritoneal dialysis apparatus with which automatic dialysis treatment can be performed by the patient himself and the operation procedures of which are very clear and easy to understand, so treatment can be performed with optimal conditions, and even if a trouble should occur, it can be coped with easily.
