A light source system (20) includes an intermediary adapter (100) which mechanically connects a first light source module (20a), a first irradiation module (60a), a second light source module (20b) and a second irradiation module (60b), a first connection mechanism which connects the first light source module (20a) and the intermediary adapter (100) and a second connection mechanism which connects the second light source module (20b) and the intermediary adapter (100). The first irradiation module (60a) and the second irradiation module (60b) are interchangeably connected to the intermediary adapter (100) in the same plane of the intermediary adapter (100).