The present invention is directed to a dental treating apparatus including: a hand piece a power source (micro motor) a driving unit (motor driver) a driving state detecting unit (resistor for load detection, root canal length measuring circuit) and a controller. The hand piece drivably holds a cutting tool on a head unit. The power source drives the cutting tool. The driving unit drives the cutting tool with twist driving in which the normal rotation and the reverse rotation are repeated. The driving state detecting unit detects a driving state of the cutting tool. The controller changes at least one parameter of a rotation angle in the normal rotation, a rotation angle speed in the normal rotation, a rotation angle in the reverse rotation, and a rotation angle speed in the reverse rotation in accordance with the driving state of the cutting tool detected by the driving state detecting unit.
