An abnormality diagnosis apparatus performs an abnormality diagnosis of a system equipped with a rotary electric machine (21). The abnormality diagnosis apparatus includes: an abnormality detection section that detects an abnormality of the system; a fail-safe processing section that, when the abnormality detection section detects an abnormality, performs a fail-safe process for controlling the rotary electric machine on a safe side; an abnormality signal generation section that, when the system is in a normal state, generates a false abnormality signal assuming that an abnormality that requires the fail-safe process has occurred; and an operation check section that performs, on the basis of the false abnormality signal generated by the abnormality signal generation section, an operation check for checking whether the fail-safe process operates normally.