1. A nuclear-magnetic-resonance (NMR) inspection apparatus comprising: means for generating a static magnetic field; means for generating magnetic field gradients in first, second, and third directions normal to one another; means for generating a high-frequency magnetic field; means for detecting NMR signals derived from a subject; means for processing detected NMR signals; a section-designating unit for designating a plane including a section of the subject to be imaged; and a control unit for controlling the means for generating magnetic field gradients, the means for generating a high-frequency magnetic field, the means for detecting NMR signals, the means for processing detected NMR signals, and pulse sequences for taking an image of the section of the subject to be imaged, wherein the section-designating unit has reference objects that can be set at up to three reference points; the section-designating unit can be moved and operated in proximity to the subject disposed in said static magnetic field and said magnetic field gradients generated by the means for generating a static magnetic field and the means for generating magnetic field gradients, respectively; the means for processing detected NMR signals identifies a first plane including the middle point between two of said reference objects and whose normal vector is a vector connecting those two reference objects or a second plane including three of said reference objects in terms of reference spatial coordinates; and the control unit controls the means for generating magnetic field gradients so that a prescribed part of said first plane or said second plane is the section of the subject to be imaged.