Abstract: A core (5) is composed of a J-shaped front core portion (1), a J-shaped rear core portion (2), a U-shaped left core portion (3), and a U-shaped right core portion (4). These core portions (1 to 4) have one-side end portions which are substantially directed in one and the same direction and which are fixed to one another to thereby form a center portion (6). A coil (7) is wound on the center portion (6). The core (5) is attached to a core support member attached closely to a patient. In use, the coil apparatus is made close or near to the patient. When the coil (7) is supplied with a pulse current, pulse-like magnetic flux is generated in the purdendal nerve and pelvic floor muscle group of the patient so that an eddy current is induced. The patient in the region where magnetic flux is generated and an eddy current is generated, is stimulated sufficiently, so that urinary incontinence treatment is performed.