An optical device includes: an excitation light source; a first light transmitter that transmits excitation light emitted from the excitation light source; a fluorescent light part that is disposed on a surface of the first light transmitter opposite a surface through which the excitation light enters, and emits fluorescent light from the excitation light; a second light transmitter that interposes the fluorescent light part with the first light transmitter, and transmits light emitted from the fluorescent light part; a light transmission fiber that guides the light exiting from the second light transmitter; and a microfabricated film that is disposed on a side of the second light transmitter closer to the light transmission fiber, and collects, toward the light transmission fiber, the light emitted from the fluorescent light part.