A cooling structure is provided that cools a rotor in a motor. The motor includes a shaft that is rotatably supported on a case and a rotor having a rotor core to which a plurality of magnets are provided on an outer periphery of the shaft and which is disposed to face a stator. Flow passages are formed on the shaft and the rotor and cooling oil passes through a core flow passage inside the rotor core from an introduction flow passage on a first side in an axial direction of the shaft and flows to the introduction flow passage on a second side in the axial direction of the shaft. An inlet communicating with the introduction flow passage and an outlet communicating with the introduction flow passage are formed in the case.