An electrical rotary machine comprises a stator having a plurality of split cores arranged in an annular shape and a holding ring capable of retaining the plurality of split cores on an inner circumferential surface so that a surface pressure is applied to an outer circumferential surface of the split cores. The electrical rotary machine further comprises a rotor provided radially inside of the stator facing the split cores in a radial direction and rotatable relative to the stator. Each of the split cores includes a tooth portion extending in an radial direction and a back yoke portion extending in a circumferential direction. Each of the split cores further includes a slit penetrating an outer circumferential periphery of the back yoke portion except for either circumferential end of the back yoke portion.