An endoscope apparatus comprising: an illumination section adapted to switch light between excitation light as first narrow-band light, second narrow-band light (NBa) and third narrow-band light (NBb) and irradiate the switched light; an image pickup section (CCD 2) that is provided in an insertion portion of an endoscope, adapted to generate a first image signal acquired through image pickup by auto fluorescence (FL1, FL2) from a tissue within a body cavity irradiated by the excitation light, generate a second image signal acquired through image pickup by return light from the tissue within the body cavity irradiated by the second narrow-band light (NBa), and generate a third image signal acquired through image pickup by return light from the tissue within the body cavity irradiated by the third narrow-band light (NBb); and an image signal generation section adapted to assign the first image signal, the second image signal and the third image signal to different colors respectively, and to generate a composite image by synthesizing the first image signal, the second image signal and the third image signal which are assigned to the different colors; characterized in that the first narrow-band light has a central wavelength of 400 nm that excites a connective tissue in a submucosa of the tissue within the body cavity to emit auto fluorescence (FL1, FL2), the second narrow-band light (NBa) has a central wavelength of 630 nm absorbed by a blood vessel running through the submucosa or a muscularis propria below the submucosa and the third narrow-band light (NBb) has a central wavelength of 600 nm absorbed by a substance locally injected into the submucosa. an illumination section adapted to switch light between excitation light as first narrow-band light, second narrow-band light (NBa) and third narrow-band light (NBb) and irradiate the switched light; an image pickup section (CCD 2) that is provided in an insertion portion of an endoscope, adapted to generate a first image signal acquired through image pickup by auto fluorescence (FL1, FL2) from a tissue within a body cavity irradiated by the excitation light, generate a second image signal acquired through image pickup by return light from the tissue within the body cavity irradiated by the second narrow-band light (NBa), and generate a third image signal acquired through image pickup by return light from the tissue within the body cavity irradiated by the third narrow-band light (NBb); and an image signal generation section adapted to assign the first image signal, the second image signal and the third image signal to different colors respectively, and to generate a composite image by synthesizing the first image signal, the second image signal and the third image signal which are assigned to the different colors; characterized in that the first narrow-band light has a central wavelength of 400 nm that excites a connective tissue in a submucosa of the tissue within the body cavity to emit auto fluorescence (FL1, FL2), the second narrow-band light (NBa) has a central wavelength of 630 nm absorbed by a blood vessel running through the submucosa or a muscularis propria below the submucosa and the third narrow-band light (NBb) has a central wavelength of 600 nm absorbed by a substance locally injected into the submucosa.