The free vibrations of the outer-clamped spinning annular disk which simulates a wafer cutting machine are investigated. The effects of the initial tension, the centrifugal force and outer-fixture extension caused by spinning on the vibration characteristics of the disk are considered. The modal parameters of the disk are calculated by using Galerkins method as the rotating speed and initial tension are varied. Laboratory experiments are also performed with a rotating and stationary disk, and, it is found that experimental and simulation results are in good agreement.