With a view to providing a magnet apparatus which can form a medium magnetic field with use of permanent magnets, the magnet apparatus having a pair of parallel disc-like permanent magnets with magnetic poles of mutually opposite polarities opposed to each other through a spacing, further comprises: two pairs of rings constituted by permanent magnets and provided respectively on pole faces of the pair of permanent magnets coaxially and doubly, the two pairs of rings each having a magnetizing direction inclined relative to a magnetizing direction of the pair of permanent magnets and having magnetic poles of mutually opposite polarities opposed to each other through a spacing; and two pairs of cylinders formed by a ferromagnetic material and partitioning the interiors of the pair of permanent magnets respectively coaxially and doubly.