[Problem] To increase the turning efficiency of a turbine and also prevent negative pressure from occurring inside a turbine chamber due to inertial rotation of turbine blades when use of a handpiece comes to an end and air suction is halted. [Solution] A handpiece comprising: a head part which has rotatable turbine blades disposed therein a neck part which is provided extending to the head part and is held by an operator and a grip part which is provided extending backward from the neck part, the handpiece further comprising an air supply pipeline which supplies air to drive the turbine blades and an air discharge pipeline which discharges air after the turbine blades are rotated, wherein a discharge-air return flow pipeline (16) is formed in the air discharge pipeline (12) and comprises: a return flow inlet (19) which opens at one end of the discharge-air return flow pipeline (16) and a discharge outlet (17) which opens in the turbine chamber (15) at the other end of the discharge-air return flow pipeline (16). The value obtained by dividing the diameter of the return flow outlet (17) of the return flow pipeline (16) by the diameter of an air supply inlet (14) of the air supply pipeline (11) is set to 1 or less, and the return flow outlet (17) of the return flow pipeline opens in the turbine chamber (15) that is close to the air supply inlet and is between the air supply inlet (14) and the discharge outlet (17).Linvention consiste à augmenter de lefficacité de rotation dune turbine et à empêcher lapparition dune pression négative à lintérieur dune chambre de turbine due à la rotation inertielle des pales de turbine lorsque laction de la pièce à main prend fin et que laspiration dair sarrête. Linvention concerne une pièce à main comprenant : une partie tête dans laquelle des pales de turbine rotatives sont disposées une partie col qui sétend à partir de la partie tête et est tenue par un opérateur une partie de préhension qui sétend vers larrière à partir de la p
