In a liquid ejection apparatus, common liquid chambers adjacent to each other and connection passages extending from the adjacent common liquid chambers are separated by a partition wall. The partition wall has a first side surface and a second side surface opposite the first side surface. The first side surface define one of side surfaces of the common chamber and one of side surfaces of the connection passage extending from the common chamber. The second side surface defines one of side surfaces of the other common chamber and one of side surfaces of the other connection passage extending from the other common chamber. The partition wall has a curved surface connecting the first side surface to the second side surface in a vicinity of a position where the connection passages having the partition wall placed therebetween are connected to each other. A curvature of the curved surface is larger than a curvature of an arc having a diameter equal to a width of the partition wall.