In order to provide a method of safely, efficiently, and industrially manufacturing fluoroaryl magnesium halide containing no impurities, such as coloring components, by a relatively gradual reaction compared with the conventional reactions, and a method of readily and efficiently manufacturing a highly-pure fluoroaryl borane derivative, fluoroaryl magnesium halide expressed by General Formula (1): where each of R1-R5 independently represents H, F, a hydrocarbon group, or an alkoxy group, provided that at least three of R1-R5 are fluorine atoms, and Xa represents Cl, Br, or I; is manufactured by reacting, in a solvent containing a chain ether solvent, hydrocarbon magnesium halide expressed by General Formula (2): R6MgXa  (2) where R6 represents a hydrocarbon group, and Xa represents Cl, Br, or I; with fluoroaryl halide expressed by General Formula (3): where each of R1-R5 independently represents H, F, a hydrocarbon group, or an alkoxy group, provided that at least three of R1-R5 are fluorine atoms and Xb represents Br or I.