PROBLEM TO BE SOLVED: To perform simultaneous observation by suppressing variation in the light quantities of special light and normal light.SOLUTION: The light source device for an electronic endoscope includes: a light source part for supplying illumination light to the electronic endoscope which has an imaging device and into which a light guide is inserted from the proximal end to the distal end a rotary plate which is disposed on the optical path of the illumination light from the light source part to the incidence end face of the light guide, and in which a transmission part for transmitting the light of a predetermined wavelength of the illumination light and a light attenuation part for attenuating the illumination light are alternately provided at each predetermined rotation angle and a switch for moving the incidence position of the illumination light to the transmission part or the light attenuation part in the radial direction of a circle of the rotary plate. The transmission part and the light attenuation part have a transmission area and a light attenuation area respectively in the circumferential direction of the circle. The light attenuation area has a light attenuation rate equalizing the transmission amount of the adjacent transmission area and the transmission amount of the light attenuation area adjacent to each other in the circumferential direction of the circle. The transmission area and the light attenuation area are provided on concentric circles whose center is the rotary axis of the rotary plate, and the wavelength of predetermined light transmitted through the transmission area has a different wavelength band for each concentric circle.
