A coolant flow path structure which cools a rotor is configured of a first coolant flow path forming a radial coolant flow path of the rotor and a second coolant flow path communicating with the first coolant flow path and forming an axial coolant flow path of the rotor, and a negative pressure structure, which brings an exist of the coolant flow path structure into a negative pressure as a result of a rotation of the rotor, is provided at the exit of the second coolant flow path.