A liquid ejection head includes an electrical wiring substrate and a printing element substrate, wherein the position variation of the printing element substrate due to curing of a sealing agent is eliminated. Specifically, a gap between two support members is covered with the electrical wiring substrate so as to be able to prevent a sealing agent from flowing into the gap. As a result, even in the case where the size of the gap varies due to the variation in the dimensional accuracy and/or the variation in the assembly accuracy, the sealing agent will not enter this gap, and therefore the shape thereof can be made substantially uniform regardless of the positions. This results in a substantially uniform stress in curing and contracting of the sealing agent, and the variation in the mounting position of the printing element substrate can be suppressed.