[Problem] When the use of the handpiece ends and inspired air is stopped, the negative pressure is prevented to being generated in the turbine room by the inertia rotation of the turbine blade, and the rotation efficiency of the turbine is improved. [Resolution approach] An air turbine handpiece comprises: a head portion with built-in free turbine blade, a neck portion installed consecutively with the head portion and grasped by an operator, a grip portion installed consecutively with the neck portion behind thereof, an air supply duct for charging air to drive the turbine blade, and an exhaust duct for exhausting the air after rotating the turbine blade. The exhaust duct 12 is provided with a reflux duct 16 for the exhausting, one end of the reflux duct is opened to the exhaust dust as an reflux entry 19, and the other end of the reflux dust is opened to the turbine room 15 as the exhaust exit17, a value in which an aperture at the reflux exit 16 of the reflux duct 16 is divided by an aperture in the air supply port 14 of the air supply duct 11, becomes one or less, and the reflux exit 17 of the reflux duct is opened to the turbine room 15 near the air supply port 14 between the air supply port 14 and the exhaust exit17.
