1. An apparatus abnormality diagnosis method of performing an apparatus abnormality diagnosis process for estimating a cause for the sign of abnormality or the abnormality by using information processing with a computer when a sign of abnormality of a target apparatus is detected or an abnormality occurs, and making an instruction for operation of the cause or maintenance operation details, wherein in a process of creating or updating an diagnosis model of the apparatus for use in the apparatus abnormality diagnosis process, at least one of apparatus event data and alarm data output from at least one of the apparatus and an external abnormality detection system is used, and the creating or updating process includes: a first process step of obtaining, in a predetermined unit of time, maintenance operation data regarding the apparatus and at least one of the alarm data and the apparatus event data; a second process step of, by using the data obtained in the first process step, creating a structured abnormality between a relevant maintenance operation and at least one of an apparatus event and alarm associated therewith as a structured abnormality model represented by a graph network structure; and a third process step of, by synthesizing the new structured abnormality model created in the second process step with a structured abnormality model created so far and recalculating a probability of occurrence among nodes updated in the graph network structure, updating the diagnosis model formed so as to include the resultant structured abnormality model.