An illumination device and an observation system capable of outputting light having a continuous spectrum and high color rendering properties are provided. Employed is an illumination device 1 including a first light source 10 that emits first-wavelength-band light L1 having a first wavelength band； a second light source 20 that emits second-wavelength-band light L2 having a second wavelength band that is broader than the first wavelength band and having a continuous spectrum； a dichroic mirror 40 that is disposed on the point of intersection of the optical axis of the first light source 10 and the optical axis of the second light source 20 and that is inserted into or removed from the optical axis of the second light source 20； and a light guide 43 that is disposed on the optical axis of the second light source 20.
