A tissue separation device includes: a sheath a tube having a deformation part a restriction member and an inner structure. The tissue separation device is used in an assembled state where the tube is movably inserted in the sheath, the restriction member is inserted in the tube, and the inner structure is movably inserted in the restriction member. The inner structure includes: wires and which are expandable and contractible an operation unit which operates expansion of the wires a tubular body and a traction shaft. The wires are expanded by being curved so as to protrude in opposite directions. When dissecting a biological tissue, the wires in an expanded state are moved within the tube in relation to the tube, without moving the tube relative to the living body.
