A device for the magneto-mechano-chemical synthesis of antitumor magnetic nanocomlex with fixed magnetic properties was developed in this work. It was estimated that changes of the induction of constant magnetic field during synthesis can significantly change magnetic properties of nanocomplex. It is also shown that nanocomplex with different magnetic properties initiated various antitumor effects on Walker-256 carcinosarcoma and after combined action of constant magnetic field and electromagnetic field. In future, the magneto-mechano-chemically individually synthesized multifunctional magnetic nanocomplex can be used for cancer magnetic nanotherapy and medical imaging functionalities for personalized cancer treatment.