A surgical treatment apparatus, comprising: an outer sheath, extending from a base portion subject to an operator's hand to a tip subject to insertion into a body cavity, that is provided with a working channel through which a treatment instrument can be passed; an image pickup device disposed at a tip portion of the outer sheath, and pivotable forceps disposed at the tip portion of the outer sheath, the pivotable forceps having a pair of forceps members that are supported on a supporting tube protruding in a direction of a central axis of the outer sheath via a joint, the pair of forceps members being configured to be capable of moving to a position away from the working channel due to the presence of the joint and arranged so as to be freely opened/closed, wherein the image pickup device is disposed so as to freely extend/retract in a duct which is disposed on an imaginary line that is parallel with an imaginary line connecting the center of a duct, in which the pivotable forceps is disposed, with the center of a duct, in which the working channel is formed, the duct being positioned on the imaginary line in an area ranging from a position corresponding to the center of the duct to a position corresponding to the center of the duct, and wherein the base portion of the outer sheath is provided with an extending/retracting operation section for extending/retracting the image pickup device, having: a mounting section mounted on the treatment instrument that is passed through the working channel, and to which the image pickup device is secured, and a connection member for guiding the movement of the mounting section with respect to the outer sheath, characterized in that the mounting section is held between two guide portions of a supporting section, the two guide portions extending in the axial direction of the insertion section, so that the mounting section extends and retracts in the axial direction of the insertion section under guidance and support of the supporting section. an outer sheath, extending from a base portion subject to an operator's hand to a tip subject to insertion into a body cavity, that is provided with a working channel through which a treatment instrument can be passed; an image pickup device disposed at a tip portion of the outer sheath, and pivotable forceps disposed at the tip portion of the outer sheath, the pivotable forceps having a pair of forceps members that are supported on a supporting tube protruding in a direction of a central axis of the outer sheath via a joint, the pair of forceps members being configured to be capable of moving to a position away from the working channel due to the presence of the joint and arranged so as to be freely opened/closed, wherein the image pickup device is disposed so as to freely extend/retract in a duct which is disposed on an imaginary line that is parallel with an imaginary line connecting the center of a duct, in which the pivotable forceps is disposed, with the center of a duct, in which the working channel is formed, the duct being positioned on the imaginary line in an area ranging from a position corresponding to the center of the duct to a position corresponding to the center of the duct, and wherein the base portion of the outer sheath is provided with an extending/retracting operation section for extending/retracting the image pickup device, having: a mounting section mounted on the treatment instrument that is passed through the working channel, and to which the image pickup device is secured, and a connection member for guiding the movement of the mounting section with respect to the outer sheath, characterized in that the mounting section is held between two guide portions of a supporting section, the two guide portions extending in the axial direction of the insertion section, so that the mounting section extends and retracts in the axial direction of the insertion section under guidance and support of the supporting section. a mounting section mounted on the treatment instrument that is passed through the working channel, and to which the image pickup device is secured, and a connection member for guiding the movement of the mounting section with respect to the outer sheath, characterized in that the mounting section is held between two guide portions of a supporting section, the two guide portions extending in the axial direction of the insertion section, so that the mounting section extends and retracts in the axial direction of the insertion section under guidance and support of the supporting section.