To detect the stacking order of a column of containers stuck in multiple stages.

A frame 41 is erected in the middle of a conveying pass for the column C, belt type lifters 43 synchronizing with each other by AC servomotors 42 and moving up and down unidirectionally from one end to the other end are arranged on the right and left of the frame 41, antennas 44 reading information on articles of RFID tags r attached to the side surfaces of the containers T are opposingly arranged to the right and left belt type lifters 43, photoelectric switches 34 detecting the column C arranged just under the frame 41 are arranged on the lower portions of the frame 41, carriage guides 46 guiding a carriage D placed with the column C are arranged on the lower inner sides of the frame 41, and a control panel 48 controlling the stacking order detector 40 is provided.