An endoscope apparatus and a method of operating the endoscope apparatus that perform both illumination light observation and fluorescence observation by a simple configuration. At least a part of a wavelength region of excitation light is included in a first wavelength region where the absorption intensity of a fluorescent material is 10% or more of a first peak value. The wavelength region of the excitation light is included in a second wavelength region where the transmittance of a first spectral transmittance characteristic is 60% or more of a second peak value and a third wavelength region where the transmittance of a second spectral transmittance characteristic is 40% or less of a third peak value. A wavelength at which intensity of fluorescence is a peak is included in a fourth wavelength region where the transmittance of the second spectral transmittance characteristic is 80% or more of the third peak value.
