A treatment instrument (1D, 1E) comprising: a rod-like ultrasound probe (30, 30E) to be inserted into a subject, for observing inside the subject; at least one sample collection portion (11D, 11E) arranged on a side face of the ultrasound probe (30, 30E); and an operation portion that operates the sample collection portion (11D, 11E), wherein the sample collection portion (11D, 11E) includes, a link portion (11Da, 11Ea) including an end supported on the ultrasound probe (30, 30E) so that the end serves as a rotation axis and the other end is pivotable relative to the rotation axis; an advancing/retracting portion (11Db, 41, 43) including an end joined to the other end of the link portion (11Da, 11Ea), the advancing/retracting portion (11Db, 41, 43) advancing/retracting in an axial direction of the ultrasound probe (30, 30E), whereby the other end of the link portion (11Da, 11Ea) pivots relative to the rotation axis, and a push rod (11Dc, 11Ec) arranged so that the push rod (11Dc, 11Ec) can advance/retract along the axial direction of the ultrasound probe (30, 30E), the push rod (11Dc, 11Ec) including an end joined to the other end of the advancing/retracting portion (11Db, 41, 43), and the other end joined to the operation portion; wherein when the advancing/retracting portion (11Db, 41, 43) is located on a most proximal end side, the advancing/retracting portion (11Db, 41, 43) and the link portion (11Da, 11Ea) are connected in the axial direction and thereby become parallel to the ultrasound probe (30, 30E), and when the advancing/retracting portion (11Db, 41, 43) is located on a most distal end side, a part of the advancing/retracting portion (11Db, 41, 43) and the link portion (11Da, 11Ea) overlap and thereby become parallel to the ultrasound probe (30, 30E); and wherein when the advancing/retracting portion (11Db, 41, 43) is located between a proximal end portion side and a distal end portion side, the link portion (11Da, 11Ea) is pushed out in a direction crossing the axial direction of the ultrasound probe (30, 30E) by the advancing/retracting portion (11Db, 41, 43), and thereby projects from the ultrasound probe (30, 30E). a rod-like ultrasound probe (30, 30E) to be inserted into a subject, for observing inside the subject; at least one sample collection portion (11D, 11E) arranged on a side face of the ultrasound probe (30, 30E); and an operation portion that operates the sample collection portion (11D, 11E), wherein the sample collection portion (11D, 11E) includes, a link portion (11Da, 11Ea) including an end supported on the ultrasound probe (30, 30E) so that the end serves as a rotation axis and the other end is pivotable relative to the rotation axis; an advancing/retracting portion (11Db, 41, 43) including an end joined to the other end of the link portion (11Da, 11Ea), the advancing/retracting portion (11Db, 41, 43) advancing/retracting in an axial direction of the ultrasound probe (30, 30E), whereby the other end of the link portion (11Da, 11Ea) pivots relative to the rotation axis, and a push rod (11Dc, 11Ec) arranged so that the push rod (11Dc, 11Ec) can advance/retract along the axial direction of the ultrasound probe (30, 30E), the push rod (11Dc, 11Ec) including an end joined to the other end of the advancing/retracting portion (11Db, 41, 43), and the other end joined to the operation portion; wherein when the advancing/retracting portion (11Db, 41, 43) is located on a most proximal end side, the advancing/retracting portion (11Db, 41, 43) and the link portion (11Da, 11Ea) are connected in the axial direction and thereby become parallel to the ultrasound probe (30, 30E), and when the advancing/retracting portion (11Db, 41, 43) is located on a most distal end side, a part of the advancing/retracting portion (11Db, 41, 43) and the link portion (11Da, 11Ea) overlap and thereby become parallel to the ultrasound probe (30, 30E); and wherein when the advancing/retracting portion (11Db, 41, 43) is located between a proximal end portion side and a distal end portion side, the link portion (11Da, 11Ea) is pushed out in a direction crossing the axial direction of the ultrasound probe (30, 30E) by the advancing/retracting portion (11Db, 41, 43), and thereby projects from the ultrasound probe (30, 30E).