Provided is an FPC, which comprises an insulating layer 2, wiring layers 3 and 4 laminated above and under the insulating layer 2, and a layer connection for connecting the wiring layers 3 and 4 electrically. The layer connection is constituted to comprise: a conductor press-fit hole 5 of a cone shape extending through the insulating layer 2 and the upper and lower wiring layers 3 and 4 and expanded to the side of one wiring layer 3; and a conductor 6 filled and press-fitted without any clearance in the conductor press-fit hole such that it is jointed to the wiring upper layer 3 deformed into the cone shape of the conductor press-fit hole 5, and is protruded from the other wiring lower layer 4 to have its surface partially coated and jointed. As a result, the contact area between the wiring layers 3 and 4 and the conductor 6 filled in the conductor press-fit hole 5 can be enlarged to retain the contact strength between the wiring layers 3 and 4 and the conductor 6 sufficiently thereby to provide a high connection reliability for the layer connection.