<p>A coil unit (10) is formed by winding an oxide superconductor wire having a band shaped surface. A residual magnetic field suppressing unit (81) is disposed within the coil unit (10). The residual magnetic field suppressing unit (81) has a through hole (HL) along the axial direction (Aa) of the coil unit (10). The residual magnetic field suppressing unit (81) is made from a magnetic body. Thus, a residual magnetic field can be suppressed.</p>
