A flexible tube (21) is constituted of a flexible tubular structure (22), a jacket (23) for covering the periphery of the tubular structure, and a coating layer (24) for coating the jacket. The jacket has a soft resin layer (29) and hard resin layer (30), and has constant thickness throughout its length. The thickness of the soft resin layer is tapered from a distal end (22a) to a proximal end (22b) of the tubular structure. The hard resin layer applied on the soft resin layer gradually thickens from the distal end to the proximal end, conversely. While an assembly (34), which includes a plurality of tubular structures coupled in series, is passing through a head section (43), two layers of the soft resin layer and hard resin layer are successively formed thereon. The assembly with the jacket is wound up after cooling. After a dust removing step, a coating layer is applied on the hard resin layer.
