The present invention relates generally to a handpiece laser treatment apparatus for treating an affected area by irradiating lasers thereto. More particularly, the present invention relates to a handpiece laser treatment apparatus capable of adjusting the drawn length of an optical fiber in which laser is irradiated. The handpiece laser treatment apparatus capable of adjusting the length of optical fiber according to the present invention comprises: a laser module for generating a laser; an optical fiber that is connected to the laser module so that the laser is irradiated to the outside; a main body in which the laser module is inserted and disposed in the inside and the optical fiber is projected forwardly; and a slider for adjusting the length of the optical fiber which is projected in front of the body.