A surgical instrument for performing incision, comprising: an incised part reception means that is configured to be inserted into a body from a skin surface area near an area subjected to treatment that has been incised in advance and configured to receive an incised part of a tendon sheath and an aponeurotic membrane, wherein the incised part reception means includes a handle portion at one end and an incision table portion with a guide groove running in a longitudinal direction at the other end; a guide fixture means that is configured to fix the incised part reception means outside the body so as to be over the area subjected to treatment, wherein the guide fixture means includes a base portion and an arm portion that extends from the base portion, and wherein the arm portion includes a slit that corresponds to the guide groove of the incised part reception means; and an incision means that is configured to perform incision under guidance of the guide fixture means, wherein the incision means has a needle that is configured to pass through the guide fixture means and to be pressed onto the incised part reception means and to be moved to incise the tendon sheath and the aponeurotic membrane, wherein the needle of the incision means is configured to be inserted from the slit of the guide fixture means and pressed onto the guide groove of the incised part reception means so as to run along the guide groove and the slit; characterized in that an oblique hole portion is formed through the base portion of the guide fixture means, wherein a knurled knob is provided at the base portion of the guide fixture means, said knurled knob being configured to fix the handle portion of the incised part reception means when being inserted into the oblique hole portion. an incised part reception means that is configured to be inserted into a body from a skin surface area near an area subjected to treatment that has been incised in advance and configured to receive an incised part of a tendon sheath and an aponeurotic membrane, wherein the incised part reception means includes a handle portion at one end and an incision table portion with a guide groove running in a longitudinal direction at the other end; a guide fixture means that is configured to fix the incised part reception means outside the body so as to be over the area subjected to treatment, wherein the guide fixture means includes a base portion and an arm portion that extends from the base portion, and wherein the arm portion includes a slit that corresponds to the guide groove of the incised part reception means; and an incision means that is configured to perform incision under guidance of the guide fixture means, wherein the incision means has a needle that is configured to pass through the guide fixture means and to be pressed onto the incised part reception means and to be moved to incise the tendon sheath and the aponeurotic membrane, wherein the needle of the incision means is configured to be inserted from the slit of the guide fixture means and pressed onto the guide groove of the incised part reception means so as to run along the guide groove and the slit; characterized in that an oblique hole portion is formed through the base portion of the guide fixture means, wherein a knurled knob is provided at the base portion of the guide fixture means, said knurled knob being configured to fix the handle portion of the incised part reception means when being inserted into the oblique hole portion.