A liquid ejection head cartridge includes a liquid ejecting head and a liquid container. The liquid ejection head includes an ejection outlet, a bubble generation region, and a movable member disposed faced to the bubble generation region and displaceable between a first position and a second position further from the bubble generation region than the first position. The movable member moves from the first to the second position by pressure produced by the generation of a bubble to permit expansion of the bubble more in a downstream side closer to the ejection outlet. The liquid container includes a substantially prism-like outer wall provided with a substantial air vent portion and having a corner, and an inner wall having a prism-like shape with outer surfaces substantially equivalent to inside surfaces of the outer wall and having a corner portion corresponding to the corner of the outer wall, the inner wall being separable from the outer wall and defining a liquid accommodating portion for containing liquid, the inner wall further having a liquid supply portion for supplying the liquid out of the liquid accommodating portion to the liquid ejection head. The inner wall has a thickness which is smaller in the corner portion than a thickness of a central portion of the outer surfaces of the inner wall.