A wavelength converter is configured to convert wavelengths of plural primary light of different wavelengths emitted from primary light sources, respectively. When a special light observation mode to emphasize and display a specific observation target in an observation target is input into a mode input circuit, a light source is configured to successively light from an aperture of a same position, the primary light sources to successively irradiate the observation target with plural illuminating light including the light whose wavelength has been converted by the wavelength converter. An image acquiring section is configured to acquire images every time the observation target is irradiated with respective illuminating light, and to generate a special light observation image of the observation target based on the images.