To perform connection of a flexible substrate and coating with protection resin almost at the same time.

When the flexible substrate 200 having a signal output electrode portion 230 formed on one end side of a base film 210 is electrically and mechanically connected, through a heat seal connection means 30, to a terminal portion 11a of a display panel 10 formed with a signal input electrode portion, a flap piece 211 formed by extending only the base film 210 from the signal output electrode portion 230 by a predetermined length along the depth of the terminal portion 11a is provided successively to the one end side of the flexible substrate 200, and a layer of protection resin 40 is formed on the flap piece 211, the flap piece 211 is heated and pressed together with the heat seal connection means 30 to cause the protection resin 40 to project from the flap piece 211, thereby coating the terminal portion 11a with the protection resin 40.