A fastening device (10) is disclosed for attaching a fluid transport circuit to an element of a structure of an aircraft, with the fluid transport circuit containing two portions (23, 42), each of which is made up of an external tube (22, 44) positioned around an internal tube (21, 43). The fastening device (10) is positioned at a connection (40) between the two portions (23, 42) of the fluid transport circuit, and contains a body (26) with a plate (27) to attach the fastening device (10) to an element (61) of the structure of the aircraft. The body (26) provides at least one sealed connection between the external tubes (22, 44) of the two portions (23, 42) and a support system provides a constant radial clearance between the internal tubes (21, 43) and the external tubes (22, 44) of the two portions (23, 42) of the fluid transport circuit.