A high‐speed rotation instrument to produce centrifugal fields greater than 100 million times gravity has been constructed. Small, solid, spherical high‐carbon chromium steel rotors are suspended magnetically in high vacuum and spun by a rotating magnetic field. It is found that the spinning rotor explodes when the calculated average value of stress in the meridian plane reaches about 1.2 times the tensile strength of the material. The maximum speed of rotation so far achieved for more than a few days without bursting was obtained with a rotor of 1.50 mm diameter. The speed of 2.11×105rev/s corresponded to a centrifugal field of 1.34×108times gravity. Our instrument will find application in the study of nuclear atomic phenomena.