An endoscope system includes an endoscope, a video processor, a power source unit, and a parameter control device. The endoscope includes an image pickup unit and an illumination unit. The power source unit supplies electric power to the image pickup unit and the illumination unit. The video processor includes an image processing unit configured to generate an endoscope image. The parameter control device includes a data collection unit, a determination unit, and a parameter determination unit. When the data collection unit acquires one or more pieces of start information during execution of electric power consumption reducing processing, the determination unit determines to stop the electric power consumption reducing processing and execute high image quality achieving processing.