Provided are: a method for rapid fluoromethylation, by which a fluoromethyl group can be easily bonded to an aromatic-ring carbon of an aromatic compound with little generation of by-products; and a process for preparation of a PET tracer using the same. The method is characterized by cross-coupling an organoboron compound in which an aromatic ring is bonded to a boron atom with FCX2Br (wherein X is ordinary hydrogen or heavy hydrogen) in a solvent obtained by adding water to an aprotic polar solvent, in the presence of a palladium complex, a phosphine ligand, and a base.