PURPOSE: To prevent any relative vibration being produced by a hydraulic pump from being transmitted via a hose.

CONSTITUTION: This coupling structure uses a coupling fitting H made up of vulcanizing and bonding a large diametral pipe 5a of a metal pipe 5, a first hose coupling 2 and a ring damper rubber part 6 solidly as one body. An external thread part 8d of a flare nut 8 is screwed in an internal thread part 10a of a mounting hole 10, while a diametral expanded pipe part 5e of the metal pipe 5 is held under pressure between the flare nut 8 and an inclined part 10b of the mounting hole 10, and a rubber hose 1 is connected to a hydraulic pump 3 via the coupling fitting H.