Abstract: A speed-up spindle unit including a non-rotative housing having a fixed ring, a sun roller secured to a high speed spindle rotatably carried in the housing and a plurality of planetary rollers rotatably carried in such a manner as to be in contact with the fixed ring at one peripheral end and the sun roller at the opposite peripheral end so that the planetary rollers individually rotate about their own axes while they revolve about the sun roller, thereby transmitting a torque from the planetary rollers to the high speed spindle through the sun roller.