To provide a device and a method for detecting, before pouring starts, any misalignment between a cope and a drag that have been molded by a flaskless molding machine and then assembled. The device (40) that can detect any misalignment between the cope (2) and the drag (3) that have been molded by the flaskless molding machine (1) and then assembled and that are being transported to the position for pouring comprises a plurality of means (51), (52), (53) for measuring distances to the cope and the drag that measures the distances (S11), (S12), (S13), (S21), (S22), (S23) to the cope and the drag, and a means (48) for calculating a degree of a misalignment between the cope and the drag on a basis of the distances to the cope and the drag that have been measured by the means for measuring distances to the cope and the drag.