Abstract: An equipment diagnosis system for diagnosing the functional state, the deterioration state, the remaining life time state, etc, of various equipment, and comprising an equipment state model portion for modelling the state of a diagnosis target equipment and for outputting information of the functional state, deterioration, remaining life time, etc, of the diagnosis target equipment on the basis of input information; stress information supply means for supplying the equipment stage model portion with appropriate information on stress which is applied to the diagnosis target equipment; comparison means for comparing information outputted from the equipment state model portion with information which is obtained on the basis of an actual maintenance result; and model correction means for correcting a parameter of the equipment state model portion on the basis of the comparison result.