A method of fluorination which comprises fluorinating a substrate by bringing the substrate and a complex compound comprising HF and a base into reaction with each other under irradiation with at least one of microwave and electromagnetic wave having a wavelength around a microwave region;
wherein the substrate is selected from the group consisting of a compound having hydrogen atom activated by a substituent at the α position, the β-position or the γ-position, a silyl ether compound, a compound having an unsaturated group, hydroxyl group, halogeno group, amino group, diazo group, triazeno group or isocyano group as a functional group, a saccharide and a cyclic compound having a three-membered or greater ring which may have a heteroatom.