A magnetic field generator includes a magnetic circuit of an open magnetic path in which a uniform magnetic field can be generated with a simpler structure. A nuclear magnetic resonance device equipped with this magnetic filed generator is also provided. The magnetic field generator of an open magnetic path type includes: a first permanent magnet and a second permanent magnet which are arranged sequentially in a reference direction with a predetermined distance therebetween while directing the direction of magnetization in the reference direction, and a third permanent magnet and a fourth permanent magnet which are arranged sequentially between the first permanent magnet and the second permanent magnet along the reference direction while being in contact with each other or being spaced apart from each other with a predetermined distance therebetween. The direction of magnetization of the third permanent magnet has a first component parallel to the reference direction and a second component intersecting a first direction orthogonally and directed toward the region side. The direction of magnetization of the fourth permanent magnet has a first component and an inverted second component opposite to the direction of the second component and having a magnitude equal to a magnitude of the second component.