The invention provides a loop winding method of a flexible pipe and a loop winding device thereof and an endoscope passage pipe. When mounting the loop composed of metal wires on the flexible pipe formed with a screw groove on a circumference, the loop is mounted reliably, thereby preventing twofold winding or job-hopping. A core-through material (10) is inserted on the flexible pipe (2), a working barrel body is tabled with the flexible pipe (2). A diameter difference of an inner circumference and the outer circumference is set as one half of the diameter, to form a state with approximately equal circle clearance along the circumference, causing the working barrel body (20) to move at a speed of below one pitch (P) of a screw groove (4) during the flexible pipe revolves for one time, to press the wire of the loop (3) at a front end of the working barrel body to be mounted in the screw groove (4).
