The flexible endoscope 20 has a flexible insertion portion 22 to be inserted in an observation zone 11 of a MRI apparatus 10. The insertion portion 22 has an inner tube 71 made of resin, triple helical tubes 72 covering the inner tube 71 and an outer tube 73 made of resin and covering the triple helical tubes 72. The triple helical tubes 72 include a first helical band 721 helically wound around an outer peripheral surface of the inner tube 71, a second helical band 722 helically wound around an outer periphery of the first helical band 721 in a direction opposite to a winding direction of the first helical band 721 and a third helical band 723 helically wound around an outer periphery of the second helical band 722 in a direction opposite to the winding direction of the second helical band 722. The first to third helical bands 721, 722, 723 are made of phosphor bronze or copper-silver alloy, which are materials having low magnetic susceptibility.