Provided is a surgical apparatus for an endoscope with which an operator can change, as desired, the size of an image of a site to be observed that appears in an endoscopic image obtained by an endoscope or the size of the range of the site to be observed. An image processing unit (zooming means) of a processor device changes a zoom magnification factor of an endoscopic image from an endoscope through electronic zooming on the basis of the operation of a foot switch. In the non-sensing region of the slider, the activation and deactivation of the zooming operation by the foot switch are switched according to a relative position of a distal end of the endoscope with respect to a distal end of the treatment tool.
