To form a composite tube having a socket extended at the end so that the tube connection is tight in the durability.

This composite tube with a socket comprises an inner tube 4, an outer tube 5 and a socket 3 formed integrally with both the tubes. The socket has a connecting part 13 having the foundation shape of a columnar state, and at least one reinforcing part 17 formed at the outside of the part 13, wherein the length (b) in the direction of the central longitudinal axis 10 compared with the thickness (a) of the reinforced part in the radial direction to the axis 10 is a≤2b.