Abstract: A method for detecting microorganisms present in a sample comprises the steps of: applying a non-lethal hydrostatic pressure to a sample containing microorganisms; and staining the microorganisms with a fluorescent dye. The method permits a significant increase in the uptake of a fluorescent substance by applying, to a sample, a desired non-lethal hydrostatic pressure, without causing any reduction of the survival rate of microorganisms. The method also permits the elimination of such a secondary effect that the subject microorganism undergoes proliferation during staining the same with a fluorescent dye. Thus, the present invention would contribute to the determination of the correct viable count in a wide variety of technical fields.