We have developed two brightness control methods for illumination and visible-light communication systems. One method is Pulse Width Modulation (PWM), the other is changing modulation depth. Using these proposed methods, we can achieve both dimmer i.e. brightness control and wireless communication at the same time. We discussed the relationship between PWM frequency, LED brightness, and communication performance. The results show that we can control brightness from 0% to 87.5% when we use PWM and data transmission possible when PWM frequency is high enough. Brightness can be controlled from 0% to 100% and communication performance is better than that of PWM when we change modulation depth.