A light source device for use in a medical apparatus has a turnable or linearly movable member or flange provided in a housing, and an actuator removably attached to the movable flange and carrying two light sources thereon. The actuator has two connector plugs provided thereon which are connected to the two light sources respectively, while the movable member is provided with two corresponding connector sockets. The two connector plugs and the corresponding two connector sockets are coupled and separated together when the actuator and the movable member are coupled and separated together. The device further comprises light conductor means for guiding light from one of the light sources to an object to be illuminated, and switch means connected between a power source and each connector socket. The device is arranged such that one of the two light sources is positioned opposite to the inlet of the light conductor means by moving the movable member coupled with the actuator. The switch means connected to the light source positioned opposite to the light conductor inlet is then closed and power is supplied from the power source to such light source. Thus, according to the invention, light sources can be easily and rapidly set to the device.