A light therapy device includes a main body, a light-emitting portion and a power supply unit. The light-emitting portion is disposed on the main body. The light-emitting portion has a first light source. The first light source provides light with a specific wavelength and with an energy ranged from 0.01 J/cm2 to 10 J/cm2. The power supply unit is electrically connected to the main body, and is configured for providing the light-emitting portion with electric power. The light therapy device is used to irradiate teeth and periodontal cells, which can accelerate regeneration of teeth bone cells and gum tissues and inhibit bacteria, thereby achieving the therapeutic effect.
