A rotor is connected to a shaft member and rotates about a central axis. The rotor includes a shaft hole having at least part of the shaft member disposed therein; and flow paths disposed around the shaft member and penetrating the rotor in a direction parallel with the central axis. Each flow path has a first surface facing outward in the radial direction; a second surface disposed outward of the first surface in the radial direction and facing the first surface; a third surface connecting the first and second surfaces at one end in a rotational direction about the central axis; a fourth surface connecting the first and second surfaces at the other end in the rotational direction. The condition C