PROBLEM TO BE SOLVED: To provide an imaging system capable of accommodating to a case when observation is performed by switching illumination light, and forming an image of the quality easy to observe and no conspicuous noise.SOLUTION: An imaging system that switches between first illumination light by a narrow band filter group 6 and second illumination light by a broad band filter group 7 to illuminate the body cavity of a patient 9, includes an AGC circuit 47 for amplifying an imaging signal imaged with a CCD 35, and an emphasizing circuit 55 for performing contour emphasizing processing. According to the content of the contour emphasizing processing, and the information on the combination of the first illumination light by the narrow band filter group and the second illumination light by the broad band filter group, the imaging system performs a control to suppress the maximum value of a gain to amplify the imaging signal by the AGC circuit 47.
