PROBLEM TO BE SOLVED: To efficiently generate illumination light suitable for simultaneous observation by special light and normal light.SOLUTION: The light source device for an electronic endoscope includes: a light source part for supplying illumination light of an object region to the electronic endoscope which has an imaging device for imaging the object region inside the distal end part of a part to be inserted into a body cavity, and into which a light guide is inserted from the proximal end to the distal end and a rotary drum which is a hollow cylindrical member disposed on the optical path of the illumination light from the light source part to the incidence end face of the light guide of the electronic endoscope, and provided with a special light area for transmitting the light of a predetermined wavelength of the illumination light and a normal light area for transmitting the normal light of the illumination light. The special light area and the normal light area are provided at a predetermined angle to the rotary axis of the rotary drum in the circumferential direction of the rotary drum within a plane vertical to the rotary axis of the rotary drum. The rotary drum has openings at positions facing the special light area and the normal light area respectively, and the optical axis of the illumination light and the rotary axis of the rotary drum are orthogonal to each other.
