An abnormality detection device for a container stack determines stacking abnormality in a container stack on a conveyance path. A plurality of containers, each including a code display surface having container information recorded at a fixed position on a lateral outer surface thereof, are stacked with the code display surfaces positioned on the same side, thereby forming a container stack. A code reader that captures an image of the code display surface is arranged on a lateral side of the conveyance path, said conveyance path conveying the container stack with the code display surfaces oriented parallel to the conveyance direction. Read data from the code reader is input into a calculation processor that detects the position coordinate value of at least one fixed point on each of the code display surfaces and determines stacking abnormality in the container stack.