The rotating electrical machine includes a rotor that has a rotor core, a key portion formed protruding in a radial direction from an inner peripheral face of the rotor core, a stress relaxing groove, which is provided at both ends of the key portion and is formed recessed farther to a radial direction outer side than the inner peripheral face of the rotor core, and a multiple of balancing holes provided one each between each pair of a multiple of magnetic poles of the rotor core, wherein lengths from a center of the rotor core to a center of each of the multiple of balancing holes are such that a length of a first straight line that passes through a center of the key portion is less than a length of an nth straight line that intersects with the first straight line vertically.