The present invention provides a previously unattainable compact and high thrust electromagnetic stirrer coil, that is, an electromagnetic stirrer coil for stirring molten steel in a mold by electromagnetic force, in which electromagnetic stirrer coil a space factor of the yoke sectional area with respect to an inside area in a vertical cross-section of said electromagnetic stirrer coil is 0. A candidate database includes self-assessment data and narrative data. The DtBu18C6 may be present from approximately 0. The antenna also includes a planar balun formed on a second side of the substrate. The controller adjusts a moving range of the focusing lens group in accordance with a degree of reliability of the phase-difference in-focus position.