A cooling structure is provided for a dynamo-electric machine. The cooling structure has a refrigerant supply path for introducing a refrigerant into a rotor, and refrigerant outlets that are opened to the refrigerant supply path so that the refrigerant will be splashed onto the coil ends of a stator as the rotor rotates. Blocking wall members are provided in refrigerant splash paths between the refrigerant outlets and the coil ends for blocking a portion of the refrigerant, which splashes from the refrigerant outlets when the rotor rotates. The rate at which the blocking wall members shield the coil ends against the refrigerant is low when the rotor rotates at a low speed and is high when the rotor rotates at a high speed.