To prevent a gasket from slipping off in attaching so as to improve work by locking the gasket on a transport pipe for fluid, to be applied to a fluid passage for fluid fuel lubricating oil, cooling water, or the like of an engine or a fluid passage for fuel, cooling media, or the like of a heating device, a refrigerator, a compressor, or the like through an I-joint, concerning a passage connecting part structure.

A seal part 16 to be mounted between an I-joint 2 and a member to be connected 30, a seal part 16a to be mounted between the I-joint 2 and the head part of an I-joint attaching bolt 28, and a connecting part 20 bridged between both gaskets 16, 16a across the I-joint 2 are provided on a gasket 13 to be used when a fluid transporting pipe 4 is connected to the member to be connected 30 through the I-joint 2, and a locking part to be locked on the I-joint 2 side is formed on the connecting part 20.