An applicator attachable to a skin treatment device that is capable of simultaneously applying RF energy and optic energy to a patient's skin, and a skin treatment method using the applicator are developed. The skin treatment device comprises: a housing, one or pair of electrodes arranged inside of the housing for generating the high frequency waves, a suction cavity formed in front of the electrodes while it is contacting to the patient's skin, opposite end installed to the housing and an lateral vacuum pocket that is connected to a flow pathway connected to a vacuum system for generating negative pressure inside the applicator. Thus, the patient's skin is lifted by suction force to place between the pair of electrodes for easily and effectively penetrating the laser beams in to the dermis.