Abstract: A coupling apparatus interconnects a first circular tube and a second circular tube which are perpendicular to each other so as to form a T-shaped tube unit. The coupling apparatus includes a first resilient securing member, a second resilient securing member and a bolt. Each of the first and second resilient securing members has a convex side surface, a concave side surface, a central hole and a plurality of radial projections. The first resilient securing member includes an internally threaded circular tubular projection projecting axially from a central portion thereof. The second resilient securing member includes a circular tubular projection projecting axially from a central portion of the convex side surface thereof. The first resilient securing member is first press fitted in an end portion of the first circular tube. The second resilient securing member is then press fitted in the end portion of the first circular tube to abut against the concave side surface of the first resilient securing member.