[en] In the atomic spectra, the subtle separation and shift between isotopes that reflect the spin and nuclear magnetic moment of nuclei appear. As one of them, there is hyperfine structural anomaly due to the difference in the magnetization distribution between the isotopes of nuclei. As for "1"1Be, which is one-neutron halo nucleus, most of its magnetization is shouldered by halo neutrons, so it is possible to detect the spread of halo neutrons by determining the hyperfine structure anomaly using an electromagnetic probe. To determine the hyperfine structure anomaly, it is necessary to measure the nuclear magnetic moment and magnetic dipole hyperfine structure constant, each independently and precisely. This time, the authors captured the "1"1Be obtained by nuclear spallation reaction into a linear Paul trap using SLOWRI prototype equipment, and applied the laser-microwave double resonance method to the "1"1Be"+ after laser cooling. Thus, the magnetic dipole hyperfine structure constant was determined as A_1_1 = -2677.302988 (72) MHz. (A.O.)