A treatment device for an endoscope comprising: a needle pipe having flexibility and formed in an elongated shape; a hollow shape section having an inner cavity formed in a distal end section of the needle pipe, and a side hole that is formed on an outer side surface of the needle pipe and communicates with the inner cavity; a piercing section provided closer to a distal end side of the needle pipe than the hollow shape section; a collection member housed in the inner cavity and includes a first cup section that opens toward a radial outer side of the needle pipe and a cutting edge section that is a periphery of the first cup section and is configured to protrude and retract between a position at which the cutting edge section is housed in the hollow shape section and a position at which the cutting edge section protrudes from the side hole; and an operating member including a distal end portion connected to the collection member, the operating member being provided so as to be advanceable and retractable relative to the needle pipe, wherein the cutting edge section protrudes from the side hole when the operating member is displaced relative to the needle pipe, characterized in that the collection member is mounted in the needle pipe via a rotation shaft, and is rotatable around the rotation shaft, and the treatment device further comprises: a sheath into which the needle pipe is inserted so as to be advanceable and retractable; and an outer blade provided at a distal end section of the sheath and configured to cut tissue collected by the collection member, wherein the outer blade is configured to advance toward the first cup section, and the outer blade is configured to cut the tissue from an opposite side of the cutting edge section. a needle pipe having flexibility and formed in an elongated shape; a hollow shape section having an inner cavity formed in a distal end section of the needle pipe, and a side hole that is formed on an outer side surface of the needle pipe and communicates with the inner cavity; a piercing section provided closer to a distal end side of the needle pipe than the hollow shape section; a collection member housed in the inner cavity and includes a first cup section that opens toward a radial outer side of the needle pipe and a cutting edge section that is a periphery of the first cup section and is configured to protrude and retract between a position at which the cutting edge section is housed in the hollow shape section and a position at which the cutting edge section protrudes from the side hole; and an operating member including a distal end portion connected to the collection member, the operating member being provided so as to be advanceable and retractable relative to the needle pipe, wherein the cutting edge section protrudes from the side hole when the operating member is displaced relative to the needle pipe, characterized in that the collection member is mounted in the needle pipe via a rotation shaft, and is rotatable around the rotation shaft, and the treatment device further comprises: a sheath into which the needle pipe is inserted so as to be advanceable and retractable; and an outer blade provided at a distal end section of the sheath and configured to cut tissue collected by the collection member, wherein the outer blade is configured to advance toward the first cup section, and the outer blade is configured to cut the tissue from an opposite side of the cutting edge section. a sheath into which the needle pipe is inserted so as to be advanceable and retractable; and an outer blade provided at a distal end section of the sheath and configured to cut tissue collected by the collection member, wherein the outer blade is configured to advance toward the first cup section, and the outer blade is configured to cut the tissue from an opposite side of the cutting edge section.