There are provided a radiofrequency device for increasing amount of a bioactive substance in a plant cell and a plant cell culture method for increasing amount of useful intracellular secondary metabolites by using the radiofrequency device. The cell culture method of the present invention makes it possible to increase specific secondary metabolites such as daidzein, equol, and the like in a cell and thus can be used for development into various medicines, agricultural pesticides, spices, pigments, food additives, and cosmetics containing bioactive substances. Further, the cell culture method of the present invention improves conventional cell culture methods limitedly used for specific cells or specific metabolites for increasing amount of intracellular bioactive substances and thus can be widely applied to production of cells and secondary metabolites.