A pressure cleaning vessel is connected to a vacuum chamber by way of a connecting pipe in the sterilizing and cleaning equipment that utilizes a supercritical fluid. The objects to be treated are impregnated, for a given period, in the supercritical fluid with which the pressure cleaning vessel has been filled. Thereafter, the connection between the pressure vessel and the vacuum chamber is opened so as to generate sudden bubbling within the vessel as a result of a large pressure difference. Thorough sterilization is achieved at the time when the supercritical fluid having penetrated into bacteria and viruses suddenly explodes and destroys these organisms instantly by vaporization and expansion.