An illumination device (1a) includes a light source unit (21) which is provided on the base end side of an insertion portion (2) to emit excitation light, a first optical transmission unit (24) which is provided from the base end side toward the front end side in the insertion portion (2) to guide excitation light from the light source unit (21) to the front end side, a fluorescent member (22) which is provided at the front end of the first optical transmission unit (24) and is excited by excitation light to emit illumination light, and a light determination unit (30) which is provided near the fluorescent member (22) to determine the amount of illumination light emitted from the fluorescent member (22) and output a determination signal. With this configuration, when laser light is irradiated from the light source unit (21) onto the fluorescent member such that illumination light is emitted from the fluorescent member (22) and is irradiated to the outside, it is possible to provide an illumination device (1a) and an endoscope apparatus (1) capable of quantitatively evaluating the amount of illumination light accurately.
