PURPOSE: To manufacture a flexible wire easily and at a low cost by forming at least two among an inner layer coil, intermediate coil, and an outer layer coil from shape memory alloy.

CONSTITUTION: Three metal coils are prepared, and at least two among them is made of shape memory alloy, and the rest is wound in the opposite direction to the above-described two coils. Then, two coils which are wound in the same direction are formed into an inner layer coil 11 and an outer layer coil 13, and one metal coil which is wound in the opposite direction is formed into an intermediate coil 12. When the inside diameter of the outer layer coil is set to A, the outside diameter of the intermediate coil is set to B1, and the inside diameter of the intermediate coil is set to B2, and the outside diameter of the inner layer coil is set to C, the coil made of shape memory alloy is shape-memorized so that the relations A≤B1, and B2≤C are satisfied. These coils are superposed by contracting or spreading the diameter, and a triple structure in which the inner layer coil 11, intermediate coil 12, and the outer layer coil 13 are superposed in succession from the inside is obtained, and the shape of the coil made of the shape memory alloy is restored at the temperature over the transformation temperature of the shape memory alloy.