PURPOSE: To prevent folding plates from colliding with articles and improve packaging conditions by providing a means for judging errors between article and preset sizes and a control means for correcting distances between the folding plates using a means for adjusting the distances therebetween.

CONSTITUTION: After presetting prior to packaging the distances S167, S169, S171, S173, M167, M168, M171, M172 and M175 between each of folding plates 167-176 in accordance with the sizes L, W and H of an article 500, the errors between the size W of the article 500 and the preset sizes are detected to judge whether or not they are within the allowable tolerances. If they are found to be outside the allowable tolerances, the distances M167, M168, M171, M172 and M175 are corrected based on the detected signal.