A horizontal continuous casting apparatus includes a fluid supply pipe for supplying a lubricating fluid to the hollow portion of the mold, which is arranged on one end side of the mold; and, a cooling water cavity for accommodating cooling water cooling an inner peripheral surface of the hollow portion of the mold, which is formed outside the inner peripheral surface, wherein the inner peripheral surface and the inner bottom surface of the cooling water cavity facing the inner peripheral surface form parallel surfaces with each other, and a cooling wall of the mold between the inner peripheral surface and the inner bottom surface is formed so that the heat flux value per unit area from the molten aluminum alloy to the cooling water is 10×105 W/m2 or more.