Disclosed herein is a bidirectional alternating application system for preventing or treating a brain tumor caused by malignant glioma cells in animals. The bidirectional alternating magnetic field application system can apply a magnetic field having weak intensity and low frequency to patients in need of the prevention or treatment of brain tumor to thereby specifically inhibit the proliferation and mobility of glioma cells without causing any damage to normal cells. Thus, the bidirectional alternating magnetic field application system can greatly reduce side effects occurring in patients after surgery.