A drive motor of a dental handpiece for driving a cutting tool of the handpiece is provided that is connected to the dental handpiece on its front end side and includes a cylindrical casing; a rotor unit, which is rotatably supported inside the casing and outputs a driving force; a stator unit provided around the rotor unit inside the casing; and an air path which causes cooling air supplied from the rear end side of the drive motor to pass through an airtight cooling room circumferentially extending between the stator unit and the casing, and to be discharged from the rear end side.