An endoscope according to the invention includes a red component cut optical filter having a characteristic that a spectral transmittance becomes half at 630 nm and zero at 670 nm, for example between a light source and an infrared cut filter, to remove a long wavelength component mainly in a red band of illumination light. This restrains scattering of light on a long wavelength side of red light, and allows taking images of mucosa, blood vessels, and other tissue in good contrast in an object to be observed and satisfactorily observing them on a monitor. Further, reduction in light amount resulting from cutting a red component with the filter is eliminated by light amount control with an aperture and gain control of a signal.