PROBLEM TO BE SOLVED: To provide a shaft coupling capable of suppressing degradation in performance even if relative displacements of two rotary shafts with respect to an axial direction increase.SOLUTION: A shaft coupling which is a shaft coupling for coupling a first rotary shaft to a second rotary shaft, comprises: a diaphragm coupling including a first member fixed to the first rotary shaft and a second member coupled to the first member via a diaphragm; and a holding device holding the second member and the second rotary shaft on a boundary between the second member and the second rotary shaft so as not to change relative positions of the second member and the second rotary shaft with respect to an axial direction.
