An electronic device and volume adjusting method detect ambient light and generate corresponding intensity signals via a sensor. Programs in a storage device, executed by at least one processor, cause the at least one processor to receive and sample light intensity signals and determine whether the ambient light level is changing. Time passing is counted if the ambient light level is changing, until the ambient light level stops changing. The counting of time stops when ambient light level stops changing and the counted time period is compared with a preset time period, a longer time period causes a volume adjusting command to be sent to a playback output device.