The electromagnet apparatuses generate a homogeneous magnetic field in a homogeneous magnetic field region by a pair of superconductive main coils for facing to each other; a pair of superconductive shielding coils for facing to each other and passing a current in a direction reverse to that of the main coils; and a pair of first ferromagnetic members for facing to each other, and the apparatuses further include a pair of second ferromagnetic members for facing to each other and be disposed in contact with or adjacent to an opposite side of the region side of the first ferromagnetic members, wherein the region is interposed between the main coils, between the shielding coils, between the first members whose outer periphery is a circle, and between the second members whose outer periphery is a circle whose diameter is larger than that of the circle of the first members.