An insert (cover member) is formed of an iron-based alloy. A casting mold is constituted by a fixed mold and a movable mold. An insert housing portion (cover housing portion) for housing the insert is formed in a separation surface between the fixed mold and the movable mold, and a magnet is embedded in the insert housing portion of either the fixed mold or the movable mold. A robot grips the insert with a gripping portion (hand) to convey the insert to a position facing the insert housing portion, releases the insert at the facing position in a state where a predetermined clearance is secured between the insert and the insert housing portion, and causes the insert to be attracted to the insert housing portion by the magnet.