The present invention is related to a novel method of detecting mRNA, based on the fact that the newly synthesized mRNA is confined inside the cell nucleus. According to the novel method cells are captured on a membrane and then treated by a cell membrane permeation solution, thereby increasing permeability of cell membranes. After the cytoplasm is washed away, nuclei are dissolved with a cell dissolving solution, and then mRNA can be successfully recovered from the obtained solution.