Peri-implantitis treatment device and method for adjusting biofilm activity

A peri-implantitis treatment device (1) according to the present invention includes: an electrode (14) for applying a negative electric potential to a metal portion (7) of a dental implant (8); a potential controller for controlling the electric potential of the electrode (14); and a mouthpiece (2) that holds the electrode (14) and the potential controller and is attached to the dental implant (8). The peri-implantitis treatment device (1) according to the present invention makes it possible to effectively inactivate even bacteria (colonies) that have formed biofilms hard to inactivate by antibiotics in deep periodontal pockets where mechanical cleaning is difficult.