To provide an expansible endoprosthesis capable of preventing a muscular tissue from entering a gap of a net shape material so as to not only make a trauma but generate a turbulent flow in a blood stream.

The endoprosthesis includes an extensible tubular mesh covered with a plastic or elastomer extensible film. A tool for positioning the endoprosthesis includes a tulip-shaped housing 4 and a tube-shaped guide 8 provided at its distal end of the same. Cutting threads cause the housing 4 to open longitudinally into several petal-like parts. The endoprosthesis is sutable to endoluminal treatment of aneurisms and dilations for a medical use.