To maintain the productivity of a production line approximately equal to or higher than before while effectively suppressing an increase in installation space and installation scale.

The depth d of a valley part 23a is set approximately to such one that a receiving table 23 does not interfere with a stock member 31. The receiving table 23 is raised to z ≥ z0 by the position control of a lifting mechanism 21. A symbol z denotes the positional coordinate of a receiving surface 22a in the vertical direction, and a symbol z0 denotes the positional coordinate of a supporting surface 31a in the vertical direction. The relation of the positional coordinates is examined with respect to a magnitude. When the result is z < z0, the rising operation of the receiving table 23 by the lifting mechanism 21 is continued and when z ≥ z0, a retraction instruction is transmitted to a slave task positionally controlling the stock member 3. Based on the retraction instruction, the stock member 31 is move in a retracted state. The problems above can be reasonably solved by, for example, periodically, continuously, and efficiently operating the stock member.