PURPOSE: To apply the fracture preventing coil characteristic to a single flexible tube by discontinuously welding coil wires of the flexible tube in the axial direction.

CONSTITUTION: Fixing sections 61 discontinuously welding coil wires are formed on the outer face of a flexible tube 10. The fixing sections 61 can be formed when the laser light is intermittently radiated in the axial direction with the base end face 45 of the flexible tube 10 serving as a start point. The pitch of the fixing sections 61 of the flexible tube 10 is changed in two stages along the axial direction of the flexible tube 10, the pitch is made small for a base end section 10a on a flexible tube support member 14 side, and the pitch is made large for an intermediate section 10b continued to the base end section 10a. The length of the unwelded portion is made short for the base end section 10a and long for the intermediate section 10b, elasticity differs according to the length of the unwelded portion, and the elasticity of the base end section 10a is made larger. The base end section 10a has large elasticity, a fold generation section 46 serving as an extraction end from the flexible tube support member 14 is reinforced to prevent fracture, thus this portion is not required to be reinforced by a fracture preventing coil.