A distal portion of an electronic endoscope is formed with a cutaway portion and a distal end surface. The distal portion is provided with side-viewing and front-viewing capturing optical systems. The side-viewing capturing optical system has a side-viewing objective lens, a prism with a half mirror surface, and a varifocal lens. Light incident on the half-mirror surface from the side-viewing objective lens is reflected to be incident on a CCD through the varifocal lens. Moving the varifocal lens allows the side-viewing capturing optical system to switch from normal observation to magnifying observation and vice versa. In the magnifying observation, a best focus position resides on an extension, of an outer circumferential surface of the distal portion, facing the cutaway portion.