Small diameter active bending catheter which is actuated by hydraulic suction mechanism for intravascular minimally invasive diagnosis and therapy has been developed. The catheter is made of a Ti-Ni super elastic alloy (SEA) tube which is processed by laser micromachining and a silicone rubber tube which covers the outside of the SEA tube. The processed SEA tube consists of a line of rings connected with meandering beams. The active catheter is filled with water and its bending angle is controlled from outside the body by suction of the water. The tip of the silicone rubber tube functions as a valve and closes by initial suction of the water, and the catheter is bent by subsequent suction. External diameter of the fabricated bending active catheter is 0.94 mm and the internal diameter is 0.85 mm. Inner space of the catheter functions as a working channel for insertion medical tools and fluids. The active catheter is effective for insertion in branch of blood vessel which diverse in acute angle which is difficult to proceed, and selective embolization of arteries for treatments tumors. The bending mechanism can be used safely in blood vessel because of its simple structure and materials which is assessed for medical use.