A wavelength variable light source apparatus includes a light source slot section for generating laser light and a main control section into which the light source slot section is inserted and which is connected to the light source slot section. The main control section optionally varies a wavelength and an output level of the laser light from the light source slot section. An optical connecting mechanism between the light source slot section and the main control section supplies the main control section with a part of laser light from the light source slot section.