To provide a treatment device using laser capable of applying the laser beam to an area of wide range of an irradiated skin surface by a single laser light source.

This treatment device is provided with an optical path converting part 5 composed of a first reflector 5a mounted on an optical axis 4 of a focusing lens 3 for reflecting the laser beam 2 in the direction to be separated from the optical axis 4, and a second reflector 5b mounted to reflect the laser beam 2 reflected by the first reflector 5a to the irradiated skin surface 7, and an optical path rotating driving part 20 composed of a rotor 20a for rotating the optical path converting part 5 approximately on the axial axis 4, and a driving device 20c for rotating the rotor 20a, whereby the laser beam 2 can be applied to the area of wide range of the irradiated skin surface on the optical axis 4 of the focusing lens 3.