A liquid ejection head comprising: a substrate; a liquid flow passage formed on the substrate and configured to allow a first liquid and a second liquid to flow inside, the liquid flow passage including a pressure chamber; a pressure generation element configured to apply pressure to the first liquid in the pressure chamber; and an ejection port configured to eject the second liquid, wherein the substrate includes a first inflow port configured to allow the first liquid to flow into the liquid flow passage in a direction (z) crossing the liquid flow passage, and a second inflow port configured to allow the second liquid to flow into the liquid flow passage, the first inflow port is located at a position closer to the pressure chamber than the second inflow port is, the first liquid and the second liquid flowing into the liquid flow passage flow in the liquid flow passage toward the pressure chamber, an interface on which the first liquid and the second liquid are in contact with each other is formed in the liquid flow passage, in a case where a length of the first inflow port is defined as L and a length of the liquid flow passage above the first inflow port is defined as W, in a direction (x) orthogonal to a direction (y) of flow of the first liquid in the pressure chamber and to a direction (z) of ejection of the second liquid from the ejection port, the liquid ejection head includes a portion that satisfies a relation defined as L ≥ W, and in a case where the direction (z) of ejection of the second liquid is a direction from bottom to top, the second liquid flows above the first liquid. a substrate; a liquid flow passage formed on the substrate and configured to allow a first liquid and a second liquid to flow inside, the liquid flow passage including a pressure chamber; a pressure generation element configured to apply pressure to the first liquid in the pressure chamber; and an ejection port configured to eject the second liquid, wherein the substrate includes a first inflow port configured to allow the first liquid to flow into the liquid flow passage in a direction (z) crossing the liquid flow passage, and a second inflow port configured to allow the second liquid to flow into the liquid flow passage, a first inflow port configured to allow the first liquid to flow into the liquid flow passage in a direction (z) crossing the liquid flow passage, and a second inflow port configured to allow the second liquid to flow into the liquid flow passage, the first inflow port is located at a position closer to the pressure chamber than the second inflow port is, the first liquid and the second liquid flowing into the liquid flow passage flow in the liquid flow passage toward the pressure chamber, an interface on which the first liquid and the second liquid are in contact with each other is formed in the liquid flow passage, in a case where a length of the first inflow port is defined as L and a length of the liquid flow passage above the first inflow port is defined as W, in a direction (x) orthogonal to a direction (y) of flow of the first liquid in the pressure chamber and to a direction (z) of ejection of the second liquid from the ejection port, the liquid ejection head includes a portion that satisfies a relation defined as L ≥ W, and in a case where the direction (z) of ejection of the second liquid is a direction from bottom to top, the second liquid flows above the first liquid.