A rotor disk for a rotor of a synchronous reluctance machine consists of a disk body material with high magnetic permeability. In order to improve the ability of the rotor disk to stand centrifugal and thermal loads, spokes extending in radial direction between a shaft opening and a disk periphery are provided with spoke openings. These openings extend over a wide distance both in circumferential direction and in radial direction to worsen the heat conducting properties of the spokes and to render the spokes less stiff.