A light source device 20 of an endoscope is provided with a light guide connector 24 for inserting a light guide plug 15. A ball lens 30 (light intensity distribution transforming element) is received in an end portion on a condenser lens 23 side of the light guide connector 24. The ball lens 30 transforms the intensity distribution of a converging flux of light coming from the condenser lens 23 such that the intensity distribution is lowered at the central area and raised at the peripheral area. A ball lens 31 (light arresting element) is received in an end portion of the light guide plug 15. The ball lens 31 arrests the light coming from the ball lens 30 and makes incidence of such arrested light to an incident end face of the light guide 16. Owing to this feature, the inserting operation of the light guide plug can be performed with ease and without a need of strict accuracy. <IMAGE>
