An integrated electromyography probe configured to be inserted into a body organ to obtain a biosignal, said probe comprising: an insertion portion insertable into a body organ; a projecting portion that is exposed to an outside of a body after the insertion portion is inserted into the body organ, wherein an end of the projecting portion is divided into two parts by a division groove and wherein the projecting portion comprises: in a peripheral surface thereof, a first groove configured to receive a push-in protrusion of an extension arm member of an external-device coupler and configured so that, upon insertion of said push-in protrusion into the first groove, said two parts of the projecting portion are caused to force apart from each other; and a second groove configured to receive a plate of the extension arm member of the external-device coupler, when the push-in protrusion of the external-device coupler is inserted into the first groove; sensing electrodes configured to detect a biosignal when the insertion portion is inserted into the body organ and having electrode protrusions formed thereon; and a device mounting area (Z) onto which the external-device coupler is removably mounted, wherein the sensing electrodes are provided at least on an outer peripheral surface of the insertion portion, and wherein the electrode protrusions of the sensing electrodes are configured to contact coupling electrode protrusions formed on an inside of a fitting hole of the external device coupler in order that the sensing electrodes can become conductive with the coupling electrode protrusions of the external-device coupler, when the probe is inserted into the fitting hole of the external-device coupler and the push-in protrusion is inserted into the first groove. an insertion portion insertable into a body organ; a projecting portion that is exposed to an outside of a body after the insertion portion is inserted into the body organ, wherein an end of the projecting portion is divided into two parts by a division groove and wherein the projecting portion comprises: in a peripheral surface thereof, a first groove configured to receive a push-in protrusion of an extension arm member of an external-device coupler and configured so that, upon insertion of said push-in protrusion into the first groove, said two parts of the projecting portion are caused to force apart from each other; and a second groove configured to receive a plate of the extension arm member of the external-device coupler, when the push-in protrusion of the external-device coupler is inserted into the first groove; in a peripheral surface thereof, a first groove configured to receive a push-in protrusion of an extension arm member of an external-device coupler and configured so that, upon insertion of said push-in protrusion into the first groove, said two parts of the projecting portion are caused to force apart from each other; and a second groove configured to receive a plate of the extension arm member of the external-device coupler, when the push-in protrusion of the external-device coupler is inserted into the first groove; sensing electrodes configured to detect a biosignal when the insertion portion is inserted into the body organ and having electrode protrusions formed thereon; and a device mounting area (Z) onto which the external-device coupler is removably mounted, wherein the sensing electrodes are provided at least on an outer peripheral surface of the insertion portion, and wherein the electrode protrusions of the sensing electrodes are configured to contact coupling electrode protrusions formed on an inside of a fitting hole of the external device coupler in order that the sensing electrodes can become conductive with the coupling electrode protrusions of the external-device coupler, when the probe is inserted into the fitting hole of the external-device coupler and the push-in protrusion is inserted into the first groove. <EOS>