PROBLEM TO BE SOLVED: To provide technologies for the smooth shift from non-high-frequency treatment to high-frequency treatment.SOLUTION: A root-canal expanding hand-piece 10 includes: a motor driving circuit 18 for rotationally driving a file 11 by a motor 17 a high-frequency signal generating circuit 19 for outputting high-frequency signals to the file 11 and a passive electrode 22 and a root-canal length measuring circuit 20 for detecting the position of an apex. An operator selects either rotational driving of the file 11 or output of high-frequency signals by operating a setting operation part 15, so that the operator can perform the treatment of an affected part in respective operation modes by operating a driving operation part 16.
