In a special mode, a superficial layer wavelength set, a middle layer wavelength set, and a deep layer wavelength set are selected successively. Each wavelength set is composed of 3 different types of narrowband light applied successively to an internal body portion. A wavelength set table (81) specifies the number of repetitions of each wavelength set. A controller (80) controls a wavelength band switching element (64) to apply every type of the narrowband light of each wavelength set, and to apply each wavelength set for the number of repetitions specified by the wavelength set table. A CCD (33) captures images of the internal body portion under illumination of the narrowband light of the respective wavelength sets. A blood information calculation section (70) calculates oxygen saturation levels of hemoglobin in blood vessels in the superficial, middle, and deep layers based on image signals, respectively. This provides information on cancer progression.
