Abstract: A method of evaluating residual life of a heat-resistant steel member after and during service at high temperature and stress makes use of a residual life evaluation diagram which is obtained beforehand on a plurality of samples of the heat-resistant steel and which represents the relationship between the life consumption and a parameter which indicates the life consumed. The parameter may be data concerning the density of an alloy element such as molybdenum and chromium, or the state of degradation in the metallurgical structure and/or state of precipitation of carbides.