A flexible tube having a laminated multi-layer structure including an outer layer composed of a main tube body layer formed of thermoplastic synthetic resin in a predetermined thickness and a reinforcing layer provided on the inner side of the main tube body layer, and an inner layer formed of a thin film sheet of air tight and low friction material. The inner layer is formed by rolling an elongated strip of a thin film sheet into a tubular form such that opposite lateral sides of the thin film sheet are overlapped one on the other to provide a thick wall portion extending longitudinally of and at one angular position of the inner layer.