PURPOSE: To save labor force and improve stowage efficiency for a raw material stowing device in a raw material yard for an iron mill, etc., by monitoring a stack growth condition with a camera and predicting a stack bottom position in completion in accordance with image data so that the stowage position of a yard machine can be modified to match to an estimated bottom position.

CONSTITUTION: A stack growth condition involved in stowage is monitored with a stack monitoring camera to detect a real stack bottom position in the direction of the stowage width of a stack with a real stack bottom position detecting means in accordance with stack image data. A stack bottom position judging means compares the real stack bottom position with an estimated stack bottom position for a preset stowage width and judges the matching of the real stack bottom position in stowage completion to the estimated stack bottom position. If mismatching occurs, a stowage position modifying means modifys the stowage position of a yard machine to allow the matching of the bottom position in completion.