Magnetic dipole forbidden (M1) transition was studied in large helical device (LHD)and F-, Si- and Ti-like M1 transitions are successfully observed for highly ionized Ar, Kr, Mo andXe ions. The wavelengths measured in visible range for the heavy elements, which are carefullydetermined with extremely small uncertainties of 0.02～0.05 A as a standard wavelength of usualelectric dipole (E1) plasma emissions, are compared with theoretical predictions. The result showsa good agreement with recent Hatree-Fock calculation including semi-empirical adjustment. TheM1 intensity for the F-like ions is examined by analyzing the intensity ratio of M1 to E1. Densitydependence of the ratio is experimentally verified by comparing with collisional- radiative modelcalculation on level population. The M1/E1 line ratio for the F-like ions is applied to the(He~(2+)) particle diagnostics in ITER, in which a steady-state operation of burning plasmas basedon D-T fusion reaction is expected with α particle heating. Unfortunately, the present estimationsuggests a negative result for the α particle measurement because the ratio is largely enhanced bythe collisional excitation with bulk ions due to high ion temperature of ITER of 10 keV as assumedand the resultant effect of the collisional excitation with α particles becomes less. Meanwhile, theM1 transition, in particular, Ti-like WLⅢ (W~(52+)) transition (3627 A) emitted in visible range,is very useful for diagnostics of the impurity behavior and the core plasma parameters in ITER. Magnetic dipole forbidden (M1) transition was studied in large helical device (LHD) and F-, Si- and Ti-like M1 transitions are successfully observed for highly ionized Ar, Kr, Mo and Xe ions. The wavelengths measured in visible range for the heavy elements, which are carefully determined with extremely small uncertainties of 0.02 to 0.05 A as a standard wavelength of usualelectric dipole (E1) plasma emissions, are compared with theoretical predictions. The result shows a good agreement with recent Hat-Fock calculation including semi-empirical adjustment . The M1 intensity for the F-like ions is examined by analyzing the intensity ratio of M1 to E1. Densitydependence of the ratio is experimentally verified by comparing with collisional- radiative modelcalculation on level population. The M1 / ​​E1 line ratio for the F-like ions is applied to the (He ~ (2+)) particle diagnostics in ITER, in which a steady-state operation of burning plasmas based on DT fusion reaction is expected with α particle he ating. Unfortunately, the present estimationsuggests a negative result for the α particle measurement because the ratio is largely enhanced by the collisional excitation with bulk ions due to high ion temperature of ITER of 10 keV as assumed and the resultant effect of the collisional excitation with α particles less. Meanwhile, the M1 transition, in particular, Ti-like WLIII (W ~ (52+)) transition (3627 A) emitted in visible range, is very useful for diagnostics of the impurity behavior and the core plasma parameters in ITER.