Abstract: A method of evaluating a residual stress including a condition setting step of setting a processing condition of water jet peening for a processing target; an analysis step of analyzing a jet flow when a fluid is injected from a nozzle model to a processing target model in accordance with the processing condition, and obtaining a void fraction which is a volume fraction of babbles contained in a unit volume of the fluid, and a collapse fraction, which is a volume fraction of the bubbles which collapse in a unit time in the unit volume of the fluid, at each position on a surface of the processing target model; an impact pressure correlation value calculating step of obtaining an impact pressure correlation value, which is a product of the void fraction and the collapse fraction at each position; an experimental value acquisition step of obtaining an impact pressure experimental value.