To provide a fuel joint device for a high pressure fuel line of excellent maintainability and a low manufacturing cost, and capable of surely preventing fuel leak.

The fuel joint device is provided with a fuel flow in passage boss 2 having an annular seal ring 8 fitted and arranged in an annular groove 2a, a fuel delivery passage boss 3, and a fuel flow passage 5 opening on a left end surface 3a of the fuel delivery passage boss 3 from a lower end surface 2b of the fuel flow in the passage boss 2. A mounting flange part 4 having a mounting hole 4a pierced therethrough is formed sideward as one piece with a fuel joint boss 1. The fuel flow in the passage boss 2 including the annular seal ring 8 is inserted and arranged in a fuel flow passage 7 of other member 6, the mounting flange part 4 is abutted and arranged on a mounting end surface 6a of the other mounting member 6 and a bolt 9 is fastened to the other member via the mounting hole 4a of the mounting flange part 4 under this condition.