Printing head and ink jet printing apparatus which performs printing with the printing head

An electrode wiring line is formed on a supporting board which supports a printing element board constituting a printing head, and it is connected with the electrode wiring lines of a flexible board, thereby to interconnect electrode wiring lines which are formed on both the sides of the printing element board in order to feed a signal or the like of identical sort. Thus, a region for the electrode wiring line on one side of the flexible board can be omitted, with the result that the number of the wiring lines of the flexible board can be increased, or the density of these wiring lines can be heightened.