NOVELTY - The method involves detecting (S1) particle number of abrasion powder contained in the oil that flows through circulation line. A determination (S2) is performed to check whether the detected particle number of abrasion powder exceeds a threshold value. A particle number ratio of flat particle to other shaped particles in abrasion powder is calculated (S3). The machine element in which abnormality is occurred among the machine elements is specified (S5) when the determined particle number of abrasion powder exceeds the threshold value, based on the particle number ratio.    USE - Method for performing abnormality-diagnosis of application object such as hydraulic transmission structure of wind power generator. Can also be used in hydraulic transmission structure of tidal power generator, ocean current electric power generating apparatus and river style electric power generating apparatus.    ADVANTAGE - Since the machine element in which abnormality occurs is specified based on the particle number ratio of flat particle in abrasion powder particle, the machine element which has rolling contact portion and second machine element which does not have rolling contact part are specified. Thus exact abnormality diagnosis is achieved.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an abnormality-diagnosis system.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating the abnormality-diagnosis method. (Drawing includes non-English language text)    Step for detecting particle number of abrasion powder contained in oil that flows through circulation line (S1)    Step for determining whether detected particle number of abrasion powder exceeds threshold value (S2)    Step for calculating particle number ratio of flat particle to other shaped particles in abrasion powder (S3)    Step for acquiring flat particle and spherical particle (S4)    Step for specifying machine element in which abnormality is occurred among machine elements (S5)