An embodiment of a rotating electrical machine has: a shaft rotatably mounted to rotate around a central rotation axis; a rotor carried by the shaft; a stator which supports stator windings and is arranged around the rotor to enclose the rotor therein; a cylindrical casing which encloses the stator therein; and a cooling circuit which is intended for the circulation of a cooling fluid, is obtained at the casing, has a single common inlet opening for the cooling fluid axially arranged in the centre of a lateral wall of the casing, and two helicoidal paths, each of which is a mirror-image twin of the other one, centrally originates from the common inlet opening and extends from the centre of the casing towards a corresponding end of the casing.