To prevent infiltration of water such as rain water from the exterior to the interior and to prevent leakage of pressurized gas or oil and infiltration of moisture of the outside air between the interior and the exterior of a composite insulating tube.

This composite insulating tube 3 comprizing a hollow core cylinder 1, an outer covering 2 provided on an outer circumference of the core cylinder 1, and a metallic seal part attached to an end part of the core cylinder 1 and adhesively jointed to an outer circumferential surface of the core tube end part and to an end part of the outer covering, wherein projections 9 projecting radially outward is provided on an outer surface of the end part of the outer covering to which the metallic seal part is jointed, and the adhesively jointed part of the metallic seal part with the outer circumferential surface of the core tube 1 has sealing property against gas and insulation oil while the adhesively jointed part of the metallic seal part with the end part of the outer covering 2 has watertightness.