A V-LED emits violet narrowband light. A G-LED emits green light. A filter limits wavelengths of the green light to pass green narrowband light. The V-LED and the G-LED are turned on alternately to apply the violet narrowband light and the green narrowband light alternately to an object. A complementary color image sensor has a Cy pixel and an Mg pixel, which are sensitive to both the violet narrowband light and the green narrowband light. The complementary color image sensor images the object under illumination of the violet narrowband light to output a first image signal and images the object under illumination of the green narrowband light to output a second image signal. Based on the first and second image signals, a special image, in which surface structure (surface blood vessels) and subsurface structure (subsurface blood vessels) are isolated from each other, is produced and displayed on a monitor.
