Present invention is a stent apparatus (1) in which a stent (3) to scaffold a vessel from the inside is held by a stent covering member (4) comprising: a tubular cartridge (2) expandable and contractible in radial direction, the expansion of which in axial direction orthogonal to the radial direction being restricted a stent formed of a biodegradable polymer as a tubular shape, shape memorized to an expanded size larger than an inner diameter of a target blood vessel in which the stent is to be implanted, and mounted to the tubular cartridge in contracted state and a stent covering member formed of a biodegradable polymer having elasticity as a cylindrical shape having an inner diameter to keep the stent in contracted state by holding an outer surface of the stent and, when the stent is expanded to the shape memorized shape, plastically deformed to release the holding of the stent. The stent is expanded together with the stent covering member along with expansion of the tubular cartridge in radial direction and released together with the stent covering member from the tubular cartridge by contraction of the tubular cartridge in radial direction.
