A light source apparatus 3 includes: a white LED 31 that emits light including a first wavelength band and a second wavelength band； a violet LED 37 that emits light in a third wavelength band, and a rotating disk 35 including a filter 42 that transmits light in the first wavelength band when inserted in an optical path of the white LED 31. The light source apparatus 3 also includes a rotating disk drive section 22 that changes a position of the rotating disk 35 so that if a normal observation mode is selected, the filter 42 is retracted from an optical path of the light emitted from the white LED 31, if a narrow band observation mode is selected, a filter 42 is continuously inserted in the optical path of the light emitted from the white LED 31, and if a twin mode is selected, the filter 42 is intermittently inserted in the optical path of the light emitted from the white LED 31.
