At least an inner tube (6) and an outer tube (5) of a double tube, which forms an insertion section (3) of an endoscopic injector (1), are formed of different kinds of plastic materials, and the outer tube (5) is formed of a material with a higher rigidity than a material of the inner tube (6). Thereby, there are provided an endoscopic therapeutic device such as an endoscopic injector, and a double tube for a therapeutic device, which have a good operability of, for example, an operation of projecting a needle, and can perform a stable operation for a diseased part.
