PURPOSE: To automatically prepare a program in a short time by attaching each instruction mark having the instruction information to the instructed articles which are previously arranged on a pallet and reading the mark by an image sensor and instructing a robot on the program for palletizing work from the instruction information.

CONSTITUTION: The instruction marks 24 and 25 are displayed with each position and direction of instruction information onto the upper surface of each instructed article 18. Then, the whole figure of the instructed article 18 is taken by a whole observation TV camera 19, and a controller 21 detects the position of the mark of '1', and a robot 11 is operated, and an arm 2 is shifted so that a TV camera 15 is set over the mark '1', and each '1' of the marks 24 and 25 is set within the viewfield of the TV camera 15. The instruction information of the mark 24 and each height of the marks 24 and 25 which is obtained by an article height sensor 16 are inputted into a controller 21, and the holding position and the holding direction are calculated from the direction of the longer axis 27 of the mark 24, and a program for palletizing work can be prepared automatically.