A method for manufacturing an automobile knuckle including a bearing mounting portion on which a hub bearing that rotatably supports a wheel of an automobile is mounted, a damper mounting portion which has a cylindrical shape and holds a lower end of a damper whose upper end is supported on a vehicle body at a vehicle upper side and a vehicle inner side with respect to the bearing mounting portion, and a mounting arm portion which couples the bearing mounting portion and the damper mounting portion, the method comprising: disposing one core in a main mold, the one core including a portion corresponding to a cylindrical opening which is an inner space of the damper mounting portion, a hollow opening in which an inner space in a hollow portion of the mounting arm portion is continuous with an opening formed in the damper mounting portion, the hollow portion being formed by extending a closed cross section by a predetermined length outwardly in a vehicle width direction from an outer peripheral surface of the damper mounting portion, and an arm-portion opening which is surrounded by a front arm portion of the mounting arm portion and a rear arm portion of the mounting arm portion, the front arm portion extending from the hollow portion to a front portion of the bearing mounting portion in such a manner that a low-rigidity portion is formed in the vicinity of the bearing mounting portion in the front arm portion, the low-rigidity portion having a smaller cross-sectional area and thus a lower rigidity than a portion peripheral to the low-rigidity portion, the rear arm portion extending from the hollow portion to a rear portion of the bearing mounting portion in such a manner that a low-rigidity portion is formed in the vicinity of the bearing mounting portion in the rear arm portion, the low-rigidity portion having a smaller cross-sectional area and thus a lower rigidity than a portion peripheral to the low-rigidity portion, the arm-portion opening having an opening area larger than that of the hollow opening; pouring molten metal into the main mold in a state where the one core is supported in the main mold; and solidifying the molten metal while the molten metal is removed from a portion corresponding to the cylindrical opening, a portion corresponding to the hollow opening, and a portion corresponding to the arm-portion opening in an internal space of the main mold due to the one core, to cast the automobile knuckle which is integral. disposing one core in a main mold, the one core including a portion corresponding to a cylindrical opening which is an inner space of the damper mounting portion, a hollow opening in which an inner space in a hollow portion of the mounting arm portion is continuous with an opening formed in the damper mounting portion, the hollow portion being formed by extending a closed cross section by a predetermined length outwardly in a vehicle width direction from an outer peripheral surface of the damper mounting portion, and an arm-portion opening which is surrounded by a front arm portion of the mounting arm portion and a rear arm portion of the mounting arm portion, the front arm portion extending from the hollow portion to a front portion of the bearing mounting portion in such a manner that a low-rigidity portion is formed in the vicinity of the bearing mounting portion in the front arm portion, the low-rigidity portion having a smaller cross-sectional area and thus a lower rigidity than a portion peripheral to the low-rigidity portion, the rear arm portion extending from the hollow portion to a rear portion of the bearing mounting portion in such a manner that a low-rigidity portion is formed in the vicinity of the bearing mounting portion in the rear arm portion, the low-rigidity portion having a smaller cross-sectional area and thus a lower rigidity than a portion peripheral to the low-rigidity portion, the arm-portion opening having an opening area larger than that of the hollow opening; pouring molten metal into the main mold in a state where the one core is supported in the main mold; and solidifying the molten metal while the molten metal is removed from a portion corresponding to the cylindrical opening, a portion corresponding to the hollow opening, and a portion corresponding to the arm-portion opening in an internal space of the main mold due to the one core, to cast the automobile knuckle which is integral.