Provided is a handpiece of a laser treatment device which can restrict a temperature rise of body tissues in a path from an irradiation portion to a target region more effectively than in the related art. The handpiece 10 includes an optical fiber 16 which guides laser light emitted from a pulse light source, and a revolving holder which holds a tip portion 64 of the optical fiber 16 such that the tip portion 64 is tilted with respect to a rotational axis C0 to direct an optical axis C1 of the laser light towards a target point P located on the rotational axis C0 and revolves the tip portion 64 of the optical fiber 16 about the rotational axis C0. Further, a pulse number of the pulse light source per unit time and a number of revolutions of the tip portion 64 of the optical fiber 16 per unit time are determined such that the pulse number of the pulse light source per unit time is not an integral multiple of the number of rotations of the tip portion 64 of the optical fiber 16 per unit time.
