This disclosure relates to a rotation control device for an air-drive and air-journal type dental handpiece, wherein rotation control is made by applying a braking force to an air journaled turbine for a certain time by the use of compressed air operated air timer and a closing valve. When the braking force is applied to cut off drive air to the turbine, there is produced negative pressure in the bearing mechanism by the inertial rotation of the turbine, whereupon negative pressure causes the turbine to suck dirt thereinto. There is also a danger of the operator being hurt by idle rotation of the cutting tool which is rotated together with the turbine. The device of the invention prevents effectively this kind of sucking up dirt and injury to operators.