An illumination controller adapted to control a converting circuit to convert an electric power of a DC input power source to drive a light source is provided. The illumination controller includes a dimming unit and a control unit. The dimming unit receives a dimming signal and correspondingly generates a dimming control signal according to the number of the dimming signal. The control unit controls the electric power provided to the light source by the converting circuit according to the dimming control signal, so as to adjust a brightness of the light source. Furthermore, an illumination driving system is also provided.