A dental air turbine includes a turbine blade, a rotating shaft which is integrally fixed with the turbine blade, and a pair of rolling bearings which rotatably support the rotating shaft with respect to a housing. The pair of rolling bearings are arranged back-to-back while fitting inner rings on the rotating shaft such that a preload is applied thereto. Accordingly, it is possible to reduce the sizes of the rolling bearings and to improve the moment rigidity of the rotating shaft.
