The present invention provides a precursor for producing a tissue regenerating instrument that regenerates a tissue, including: a tube made of a biodegradable material provided with a lumen in a longitudinal direction; a rod made of a biodegradable material swellable with a softening solvent, fixed to an inner wall of the tube substantially parallel to the longitudinal direction of the tube; and a fixing means that fixes the rod to the inner wall of the tube, in which the rod in a non-swelled state has a occupied cross-sectional area perpendicular to the longitudinal direction is smaller than a cross-sectional area of the lumen of the tube, and the occupied cross-sectional area perpendicular to the longitudinal direction of the rod in a saturated swelled state with the softening solvent is substantially the same as the cross-sectional area of the lumen of the tube.