To provide a connecting structure stably providing high connecting strength in bonding a metal pipe using an adhesive.

Conical and funnel-like tapered surfaces 3a, 4a are formed on the ends of the metal pipes 3, 4, respectively, and the tapered surface 3a is internally and concentrically fitted to the tapered surface 4a. The angles θ of inclination of the tapered surface 3a and tapered surface 4a are set within the range of 3-8°. Vertical annular end faces are provided from the tapered surfaces 3a and 4a, respectively, on the inner periphery side, and the annular end face 4b is provided with a ring groove 4c in which an O-ring is fitted. The tapered surfaces are made to confront with each other at a height ranging from 0.05-0.3 mm, the separating distance from the tapered surface 3a to tapered surface 4a is set from 0.05-0.3 mm, and the gap is filled with an adhesive.