Disclosed is a low-cost and resource-saving cleaning method wherein high cleaning effects are obtained by high-pressure jet cleaning or two-fluid cleaning using a gas-dissolved water. In the high-pressure jet cleaning method or the two-fluid cleaning method, a cleaning liquid or a mixed fluid of the cleaning liquid and a gas is jetted from a cleaning fluid jetting nozzle toward a subject to be cleaned, and the subject is cleaned. The cleaning liquid introduced into the cleaning fluid jetting nozzle contains the dissolved gas in a quantity equal to or more than the saturation solubility at the liquid temperature of the cleaning liquid.