A wiring pattern having a plurality of terminal lands and leads independently respectively connected therewith is formed on one face of an insulator of a flexible wiring substrate. The insulator is provided with through-holes whereby the terminal lands are exposed on the other side. The terminal lands are electrically connected and fixed on the other face of the insulator by joining with the head terminals of the inkjet head with conductive adhesive, through the through-holes. Isolation between the leads and terminal lands arranged on the one side thereof from the conductive adhesive is provided by the insulator.