The handpiece includes an outer housing of a bar shape a cylindrical core inserted into the outer housing and having an air hole and a water hole pipes respective inserted into the air hole and the water hole of the core a rotor made with a cylindrical magnetic material and inserted into the core cylindrical support rings forcedly fit to both sides of transfer shafts of the rotor a pair of bearings respectively disposed at the front side and the rear side of the support rings a coupling disposed in front of the rotor a front housing joined to the front of the outer housing a front cap disposed at the rear of the core a rear cap disposed at the rear of the front cap and having a power supply terminal disposed at one side thereof and a rear housing joined to the rear of the outer housing.
