PURPOSE: To obtain a carton that is improved in strength at four corners of side walls without providing a cover, prevents a content from becoming stuffy, and can be stacked high without a possibility of collapsing.

CONSTITUTION: A bottom piece 1 is provided in the center. End wall pieces 4, 5 and side wall pieces 2, 3 are connected to four peripheral edges of the bottom piece 1 to be respectively erectly folded through folding lines (a), (b), (c), (d) to form walls on four peripheral edges of the bottom piece. Reinforcing corner pieces 9, 10, 11, 12 are connected to both ends of the end wall pieces 4, 5 through folding lines to be folded along the inner corner parts connecting the end wall pieces 4, 5 to the side wall pieces 2, 3.