The present invention relates to a method for labelling fluorine-18, which is a radioisotope, and more specifically, to a method for labelling a [18F]fluoride in a method for preparing an organic [18F]fluoro compound by reacting an alkyl halide or an alkyl sulfonate with a [18F]fluoride, wherein a [18F]fluoride supported on a quaternary alkyl ammonium polymer support is eluted using a solution containing a metal salt or a quaternary ammonium salt with an adjusted pH, and a base is not additionally used. The present invention enables a labeling reaction without an additional base after precisely reflecting the concentration of a base absolutely necessary for the nucleophilic substitution of a [18F]fluoride or eluting a [18F]fluoride using a [18F]fluoride eluent with an adjusted pH, thereby stably obtaining a [18F]fluoride-labelled compound in a high yield, and is thus useful for production of fluorine-18-labelled radioactive medical supplies.