A magnet apparatus having two static magnetic field-generating sources constituted by current-carrying means (13 to 16) arranged concentrically to generate a uniform magnetic field directed in the first direction, each static magnetic field generating source having at least four current-carrying means. Assume that a predetermined line (18) lies in a first plane including a first axis extending in parallel with the first direction and passing through near the centers of the current-carrying means, a second axis intersecting the first axis perpendicularly and existing nearly at an equal distance from the second static magnetic field-generating source. When the geometrical center of the cross section of each current-carrying means is projected onto the predetermined straight line (18) on the first plane, the forward and reverse current-carrying directions of the corresponding current-carrying means are alternatingly arranged for each of the static magnetic field-generating sources.