In a wedge looseness diagnosis which is performed by striking wedges of a rotary electric machine, a variation of a wave form of a strike sound is reduced with respect to a variation of an amount of looseness of the wedges, and it is difficult that a slight difference of the amount of the looseness of the wedges is discriminated, so that the wedges are struck by a strike portion in a state where the wedges are pressed by a pressure portion which presses the wedges, and a strike sound at a high frequency is reduced, whereby an amount of a variation of magnitude of the strike sound is enlarged with respect to a valuation of the amount of the looseness of the wedges, and the amount of the looseness of the wedges is judged in accordance with the strike sound which is obtained by a strike sound measuring portion.