PURPOSE: To prevent the breakage of a connector or the generation of an unusual sound by attachably and detachably fixing a connector on the top end of a flat harness to a member to be fixed by a fastener cloth with female and male yarn-like locking part when the branch circuit for option of the flat harness is not used.

CONSTITUTION: When a flat harness 10 is arranged on a panel 15 in the inner part of a vehicle door, the terminal connector of a main body circuit part 13 is fitted and connected to a partner connector. Branch circuit parts 14A, 14B having no electrical equipment connected thereto are fixed to and held by the panel 15 through fastener clothes 18, 19 preliminarily stuck thereto. The breakage of a connector 17 or the generation of a foreign sound by the contact of the circuit parts 14A, 14B with the panel 15 by the vibration caused in rolling of the vehicle can be surely prevented. When an electrical equipment option is mounted later, the corresponding circuit part 14A can be easily connected thereto by the connector 17 on the top end by releasing a yarn-like locking part 20.