A normal light image and a fluorescence image are adjusted to proper brightness with a simple and inexpensive configuration. A processor 4 includes a comparison section 103 for comparing an output (dimming signal) of a dimmer circuit 40 and a predetermined reference value, a setting section 102 for setting a gain of an AGC 33, a shutter control parameter (charge storage time) in an electronic shutter control section 101, and an opening area of a light source diaphragm 13 in a light source device 3 based on a comparison result of the comparison section 103, and the electronic shutter control section 101 for controlling an electronic shutter function of a CCD driving circuit 31 under control of the setting section 102.
