1. An endoscope apparatus comprising: an observation optical system; a solid-state imaging element that is relatively positioned and fixed with respect to the observation optical system, obtains an optical image formed thereon by the observation optical system, and has a plurality of photoelectric conversion elements arrayed therein which photoelectrically convert the optical image; a memory section that stores image cutting-out information therein that specifies an image cutting-out region for a process of cutting out an image for display, which corresponds to a display area to be displayed on a monitor, from an image generated on the basis of an imaging signal of the solid-state imaging element; and an image processing section which cuts out the image for display from the image, on the basis of the image cutting-out information stored in the memory section, wherein the memory section stores the information therein for specifying the image cutting-out region for the process of cutting out the image for display, which corresponds to an overlapping region in which a displayable pixel area of the solid-state imaging element and an imaging area of the optical image to be formed on the solid-state imaging element by the observation optical system overlap one another, and overlap one another when the center of the imaging area is matched with the center of the display area, as the image cutting-out information, and the image processing section expands the image for display to an image size of the display area, when an image size of the cut-out image for display becomes smaller than the image size of the display area due to deviation between the center of the displayable pixel area and the center of the imaging area.