A forceps type treatment instrument comprising: a forceps support member that includes a first arm portion and a second arm portion attached to a distal end of a sheath and facing each other; a first forceps piece and a second forceps piece which are interposed between the first arm portion and the second arm portion of the forceps support member; and a spacer member that rotatably supports each of the first forceps piece and the second forceps piece, wherein the first forceps piece includes a first shaft hole, wherein the second forceps piece includes a second shaft hole, wherein the spacer member includes a first shaft portion (33a,33a') rotatably inserted into the first shaft hole and a second shaft portion (33b,33b') rotatably inserted into the second shaft hole, characterized in that the spacer member is provided with one of a first protrusion portion or a first notch portion and one of a second protrusion portion or a second notch portion, wherein an inner peripheral surface of the first shaft hole is provided with the other of the first protrusion portion or the first notch portion, wherein an inner peripheral surface of the second shaft hole is provided with the other of the second protrusion portion or the second notch portion, wherein the first notch portion is provided with a first end portion with which the first protrusion portion comes into contact when the first forceps piece is rotated in a first direction and a second end portion which is the other end facing the first end portion, and wherein the second notch portion is provided with a third end portion with which the second protrusion portion comes into contact when the second forceps piece is rotated in a second direction opposite to the first direction and a fourth end portion which is the other end facing the third end portion. a forceps support member that includes a first arm portion and a second arm portion attached to a distal end of a sheath and facing each other; a first forceps piece and a second forceps piece which are interposed between the first arm portion and the second arm portion of the forceps support member; and a spacer member that rotatably supports each of the first forceps piece and the second forceps piece, wherein the first forceps piece includes a first shaft hole, wherein the second forceps piece includes a second shaft hole, wherein the spacer member includes a first shaft portion (33a,33a') rotatably inserted into the first shaft hole and a second shaft portion (33b,33b') rotatably inserted into the second shaft hole, characterized in that the spacer member is provided with one of a first protrusion portion or a first notch portion and one of a second protrusion portion or a second notch portion, wherein an inner peripheral surface of the first shaft hole is provided with the other of the first protrusion portion or the first notch portion, wherein an inner peripheral surface of the second shaft hole is provided with the other of the second protrusion portion or the second notch portion, wherein the first notch portion is provided with a first end portion with which the first protrusion portion comes into contact when the first forceps piece is rotated in a first direction and a second end portion which is the other end facing the first end portion, and wherein the second notch portion is provided with a third end portion with which the second protrusion portion comes into contact when the second forceps piece is rotated in a second direction opposite to the first direction and a fourth end portion which is the other end facing the third end portion.