An adjustment mechanism that adjusts an inclination and a position of an optical axis of an excitation light optical system with respect to an optical axis of a white light optical system is provided. The adjustment mechanism includes a frame plate, a plate-shaped lever, a fixing unit, a first adjuster, and a second adjuster. The frame plate is orthogonally placed with respect to the optical axis of the white light optical system, and perforated with a pair of circular holes, and an elliptical hole. The plate-shaped lever is perforated with a first elliptical hole and a second elliptical hole and a cylindrical projection. The fixing unit fixes the excitation light optical system to the plate-shaped lever. The first adjuster includes a first supporting axle and a first disc-shaped cam to which the first supporting axle is eccentrically fixed, the first disc-shaped cam being rotatably and slidably fitted in the first elliptical hole of the plate-shaped lever. The second adjuster includes a second supporting axle and a second disc-shaped cam to which the second supporting axle is eccentrically fixed, the second disc-shaped cam being rotatably and slidably fitted in the second elliptical hole of the plate-shaped lever.