The method of manufacturing a liquid ejection head includes: forming a first protective layer on one surface of the substrate; forming the wiring layer on another surface of the substrate; forming the insulating layer on the wiring layer, and then partially removing the insulating layer to partially expose the wiring layer; forming the electrode pad on an exposed portion of the wiring layer; forming a flow path member on the another surface of the substrate; forming a second protective layer on the one surface of the substrate after the formation of the flow path member; and partially removing at least one of the first protective layer and the second protective layer, and then forming the supply port leading from the one surface of the substrate to the another surface of the substrate.